Behavioral rhythms of the Japanese newts, Cynops pyrrhogaster, under a semi-natural condition

 Locomotor activity rhythms of the Japanese newt, Cynops pyrrhogaster, were recorded under a semi-natural condition using phototransistor systems. The daily activity rhythm showed a seasonal change: the locomotor activity was mainly diurnal (active during the daytime) from spring to early summer; mainly nocturnal (active during the night-time) from summer to autumn; and showed either a diurnal or nocturnal pattern, depending on the ambient temperature, in winter. To analyze the daily activity in detail, we observed the behavior of a group of newts (three males, three females) throughout 24 h. Four types of behavior (respiration, feeding, mating, and resting on the land) were observed. Each behavior had daily rhythms and showed a seasonal change. The behavior on land showed mainly a nocturnal or bimodal pattern (activity rhythms with two peaks) throughout the year and was more frequently observed in summer. Mating behavior also showed a seasonal change: high activity in spring, with peaks in the early morning and evening, but no activity in summer. Except in winter, feeding and respiratory behavior showed no seasonal changes in either activity period or frequency. Coupling between behavior and the clock seems to be weak in the Japanese newt because of indistinct daily rhythms and frequent phase changes of locomotor activity in water. Physical factors such as humidity and temperature seem to affect strongly the daily activity of the newts. Received: 21 April 1997 / Accepted: 1 September 1997     

The seasonal characteristics of the circadian rhythm of hypoxic resistance and convulsive resistance]

Hypoxic and convulsive resistances have daily rhythms, the pattern of which depends on the year season. Latent period of occurrence of epileptic seizures and time of life at the "height" of 11,000 m above the sea level undergo similar changes in autumn and spring. In winter minimal similarity between daily dynamics of each of these resistances and analogous ones in other seasons is observed, but rhythms of tolerance to hypoxia are maximally synchronized with the rhythms of convulsive resistance. In autumn hypoxic and convulsive resistances are minimal. Maximums of these indices are observed in different seasons: for tolerance to hypoxia it is summer, for convulsive resistance--spring.     

Daily and Seasonal Rhythms in Immune Responses of Splenocytes in the Freshwater Snake,Natrix piscator

Present study was designed to examine daily and seasonal variability in the innate immune responses of splenocytes in the fresh water snake, Natrix piscator. Animals were mildly anesthetized and spleen was aseptically isolated and processed for macrophage phagocytosis, NBT reduction, nitrite production, splenocyte proliferation and serum lysozyme activity. Samples were collected at seven time points, viz., 0000, 0400, 0800, 1200, 1600, 2000 and 0000 h during three different seasons, namely summer, winter and spring. Cosinor analysis revealed that percent phagocytosis had a significant 24-h rhythm during summer and spring seasons. The peaks of rhythms in NBT reduction and nitrite release occurred in the morning hours at 10.88 h and 8.31 h, respectively, in winter. A significant 24-h rhythm was also observed in lysozyme concentration and splenocyte proliferation (both Basal and Concanavalin A stimulated) in all three seasons. A significant phase shift in splenocyte proliferation was obtained with a trend of delayed phase shift from winter to spring and from spring to summer. Of the nine variables, significant annual (seasonal) rhythms were detected in almost all variables, excluding phagocytic and splenosomatic indices. All rhythmic variables, except spleen cellularity, exhibited tightly synchronized peaks coinciding with the progressive and recrudescence phases of annual reproductive cycle. It is concluded that the snake synchronizes its daily and seasonal immune activity with the corresponding external time cues. The enhancement of immune function coinciding with one of its crucial reproductive phases might be helping it to cope with the seasonal stressors, including abundance of pathogens, which would otherwise jeopardize the successful reproduction and eventual survival of the species.     

Daily body temperature rhythms persist under the midnight sun but are absent during hibernation in free-living arctic ground squirrels

In indigenous arctic reindeer and ptarmigan, circadian rhythms are not expressed during the constant light of summer or constant dark of winter, and it has been hypothesized that a seasonal absence of circadian rhythms is common to all vertebrate residents of polar regions. Here, we show that, while free-living arctic ground squirrels do not express circadian rhythms during the heterothermic and pre-emergent euthermic intervals of hibernation, they display entrained daily rhythms of body temperature (T(b)) throughout their active season, which includes six weeks of constant sun. In winter, ground squirrels are arrhythmic and regulate core body temperatures to within ±0.2°C for up to 18 days during steady-state torpor. In spring, after the use of torpor ends, male but not female ground squirrels, resume euthermic levels of T(b) in their dark burrows but remain arrhythmic for up to 27 days. However, once activity on the surface begins, both sexes exhibit robust 24 h cycles of body temperature. We suggest that persistence of nycthemeral rhythms through the polar summer enables ground squirrels to minimize thermoregulatory costs. However, the environmental cues (zeitgebers) used to entrain rhythms during the constant light of the arctic summer in these semi-fossorial rodents are unknown.     

Seasonal affective disorder: an overview

Seasonal Affective Disorder (SAD) is a condition of regularly occurring depressions in winter with a remission the following spring or summer. In addition to depressed mood, the patients tend to experience increased appetite and an increased duration of sleep during the winter. SAD is a relatively common condition, affecting 1-3% of adults in temperate climates, and it is more prevalent in women. The pathological mechanisms underlying SAD are incompletely understood. Certain neurotransmitters have been implicated; a dysfunction in the serotonin system in particular has been demonstrated by a variety of approaches. The role of circadian rhythms in SAD needs to be clarified. The phase-delay hypothesis holds that SAD patients' circadian rhythms are delayed relative to the sleep/wake or rest/activity cycle. This hypothesis predicts that the symptoms of SAD will improve if the circadian rhythms can be phase-advanced. There is some experimental support for this. SAD can be treated successfully with light therapy. In classical light therapy, the SAD sufferer sits in front of a light box, exposed to 2000-10,000 lux for 30-120 min daily during the winter. Other forms of light treatments, pharmacotherapy, and other therapies are currently being tested for SAD.     

Daily and seasonal variations in Na+, K+, Ca2+ and Mg2+ contents in the cingulate cortex of the mouse brain

Daily changes in Na+, K+, Ca2+ and Mg2+ contents in the cingulate cortex of mice housed under controlled light/dark (LD) conditions were investigated for a 24-hour period in spring, summer, autumn and winter. The total ion content in the mineralized tissue was evaluated by absorption/emission flame spectrophotometry. In nearly all the tested cation contents significant daily concentration changes were found with a maximum in the dark phase of the LD cycle. The differences in wave form and mean cingulate cortex ion contents throughout the year suggest that the rhythms undergo seasonal variations. The functional importance of daily and anual fluctuations in the brain cation concentrations has been discussed.     

Seasonal Affective Disorder: An Overview

Seasonal Affective Disorder (SAD) is a condition of regularly occurring depressions in winter with a remission the following spring or summer. In addition to depressed mood, the patients tend to experience increased appetite and an increased duration of sleep during the winter. SAD is a relatively common condition, affecting 1–3% of adults in temperate climates, and it is more prevalent in women.

The pathological mechanisms underlying SAD are incompletely understood. Certain neurotransmitters have been implicated; a dysfunction in the serotonin system in particular has been demonstrated by a variety of approaches. The role of circadian rhythms in SAD needs to be clarified. The phase-delay hypothesis holds that SAD patients' circadian rhythms are delayed relative to the sleep/wake or rest/activity cycle. This hypothesis predicts that the symptoms of SAD will improve if the circadian rhythms can be phase-advanced. There is some experimental support for this.

SAD can be treated successfully with light therapy. In classical light therapy, the SAD sufferer sits in front of a light box, exposed to 2000–10,000 lux for 30–120min daily during the winter. Other forms of light treatments, pharmacotherapy, and other therapies are currently being tested for SAD.     

Seasonal variation in endogenous serum melatonin profiles in goats: a difference between spring and fall?

The pineal hormone melatonin serves as a signal of day length in the regulation of annual rhythms of physiological functions and behavior. The duration of high melatonin levels in body fluids is proportional to the duration of the dark period of the day. Due to the direct suppression of melatonin by light, the overt melatonin rhythm may differ from the endogenous rhythm driven by the hypothalamic circadian clock. The aim of this study was to find out possible differences between the overt and endogenous melatonin rhythms in goats during the course of a year. Seven Finnish landrace goats (nonlactating females) were kept under artificial lighting that approximately simulated the annual changes of day length at 60 degrees N. Blood samples for melatonin measurements by radioimmunoassay were collected at 2-h intervals during six seasons: winter (light:dark 6:18 h), early spring (10:14), late spring (14:10), summer (18:6), early fall (14:10), and late fall (10:14). Melatonin profiles were determined for 2 consecutive days, first in light-dark (LD) conditions and then in continuous darkness (DD). In LD conditions, the profiles matched the dark period with one exception: In winter, the mean peak duration was significantly shorter than the scotoperiod. In DD conditions, two types of endogenous melatonin patterns were found: a "winter pattern" (peak duration 13-15 h) in winter, early spring, early fall, and late fall, and a "summer pattern" (duration about 11 h) in late spring and summer. Thus, in equal habitual LD conditions in late spring and early fall (LD 14:10), the endogenous melatonin rhythms were not quite similar: The pattern in late spring resembled that in summer, and the pattern in early fall that in winter. These results suggest that, in addition to the light-adjusted overt melatonin rhythm, the endogenous rhythm of melatonin secretion varies during the course of a year.     

Seasonal modulation of the 8-and 24-hour rhythms of ondansetron tolerance in mice

Ondansetron (Zophren((R))) is a serotonin 5HT(3)-receptor antagonist used primarily to control nausea and vomiting caused by cytotoxic chemo-and radio-therapy. Tolerance to this drug shows both 24 and 8 h periodicities. In this framework, this study aimed to determine whether these ondansetron tolerance rhythms are modulated by season. The chronotoxic effect of a fixed dose (3.5 mg/kg, i.p.) of the drug was investigated with reference to both time of the day and year dependencies. Season-related studies were performed on 560 male Swiss mice, 10 to 12 wks old, synchronized with L:D=12:12 for three weeks. During a 1 yr span (2005), four 24 h studies were performed with a single dosing time at 1, 7, 13, and 19 hours after light onset (HALO), respectively. Tolerance was assessed daily during a 40-day span after acute ondansetron treatment. Both chi(2) test and cosinor methods were used to analyze the time series data. Statistically significant dosing time-dependent changes were validated in both yearly and daily time scales. The 24 h mean survival rate peaked in spring (92%) compared to fall (72%), the 20% difference being statistically significant (chi(2) test with p<0.05 and cosinor with p<0.0001 for seasonal rhythm detection and with a peak time, ?,=April 3+/-6.6 days). A 24 h rhythm was also detected in each of the seasonal time points. However, the curve pattern was monophasic in fall as well as spring. In fall, a large amplitude (A) circadian rhythm was detected that peaked at 19 HALO, while in the spring, a small circadian rhythm was detected that peaked at 1 HALO. The curve pattern was biphasic in summer (with large A) and in winter (with a small A). The existence of two peaks of equal magnitude in winter (100% survival rate) and in summer (100% and 90%) suggests the presence of both circadian and ultradian rhythms rather than an ultradian component of the 24 h period. The seasonal modulation of ondansetron circadian chronotolerance seems to involve several rhythm parameters: season-related changes in the 24 h mean (M), amplitude (A), acrophase location (?), as well as bimodal curve patterns including the coexistence of rhythms with respectively 24 and 8 h periods in winter and summer. In conclusion, tolerance to ondansetron varies not only according to the 24 and 8 h periods but also according to seasons, which suggests the complexity of ondansetron toxicity rhythms. Seasonal modulation of ondansetron tolerance may also influence the strategies of chemo-and chrono-therapy, and it is therefore necessary to take it into account in clinical drug-delivery protocols to minimize side effects of cytotoxic anticancer and antiemetic agents.     

Monthly day/night changes and seasonal daily rhythms of sexual steroids in Senegal sole (Solea senegalensis) under natural fluctuating or controlled environmental conditions

In this paper we attempted to investigate the existence of daily fluctuations on plasma sexual steroids (17beta-estradiol, E(2) and testosterone, T) in Senegal sole (Solea senegalensis) females. We described the monthly day/night concentrations and seasonal daily rhythms in animals reared under natural photo- and thermo-period. In addition, the influence of the natural annual fluctuation of the water temperature on the plasma concentration of these steroids was investigated, using one group of Senegal sole under a natural photoperiod, but with an attenuated thermal cycle (around 17-20 degrees C) for one year. Although no significant day/night differences were detected in monthly samplings, the existence of an annual rhythm of E(2) and T (p<0.01) with an acrophase in February was revealed by COSINOR analysis. Maximum values were reached in March for both steroids (6.1+/-1.7 ng mL(-1) at mid-dark, MD and 4.0+/-0.6 ng mL(-1) at mid-light, ML for E2 and 1.4+/-0.4 ng mL(-1) at MD and 0.8+/-0.1 ng mL(-1) at ML for T) in anticipation of the spawning season (May-June). As regards seasonal daily rhythms, the presence of daily oscillations was revealed. At the spring solstice (21st March) a daily rhythm was observed for both steroids (COSINOR, p<0.01), with an acrophase at 20:00 h (E(2)) and at 21:08 h (T). In summer, autumn and winter no daily rhythms were observed due to the low steroid levels at those seasons. When Senegal sole females were submitted to an attenuated annual thermal cycle, the steroid rhythm disappeared (there was no surge in spring, as in the control group) and these fish did not spawn, despite being subjected to natural photoperiod conditions. This result underlined the importance of the natural annual fluctuation of water temperature and photoperiod on the synchronization of the spawning season and on the onset of steroidogenesis.     

Seasonal changes in the thermoregulation of laboratory golden hamsters during acclimation to seminatural outdoor conditions

Proper adjustments of the thermoregulatory mechanisms ensure survival in the natural environment. In the present study, we tested the hypothesis that laboratory golden hamsters (Mesocricetus auratus) housed under seminatural outdoor conditions are able to acclimatize to daily and seasonal changes in the environment despite their long history of breeding in captivity. The animals experienced natural changes in the photoperiod and ambient temperature characteristic for central Poland. During experiments in the thermal gradient system, the daily rhythms of body temperature (measured as the temperature of brown adipose tissue, TBAT), preferred ambient temperature (PTa) and activity were measured in summer, autumn and spring. We found that mean TBAT was highest in autumn and least in summer, reflecting seasonal changes in the capacity for nonshivering thermogenesis (NST). In summer, TBAT followed the robust daily rhythm with the amplitude of 1.1+/-0.1 degrees C. This amplitude was depressed in autumn (0.2+/-0.1 degrees C) and partially restored in spring (0.4+/-0.1 degrees C). Seasonal changes in the daily amplitude of TBAT recorded during both transitional periods, i.e., in autumn and spring, seem to be associated with hamsters' hibernation. In autumn, mean daily PTa was lower than in summer and spring, indicating the lowering of a set point for core body temperature (Tb) regulation. Locomotor activity was much higher in spring than in summer and autumn, and it always predominated at night. We conclude that laboratory golden hamsters housed under seminatural conditions express daily and seasonal changes in the thermoregulatory mechanisms that, despite long history of breeding in captivity, enable proper acclimatization to seasonally changing environment and ensure successful hibernation and winter survival.     

Seasonal Modulation of the 8‐and 24‐Hour Rhythms of Ondansetron Tolerance in Mice

Ondansetron (Zophren®) is a serotonin 5HT₃-receptor antagonist used primarily to control nausea and vomiting caused by cytotoxic chemo‐and radio‐therapy. Tolerance to this drug shows both 24 and 8 h periodicities. In this framework, this study aimed to determine whether these ondansetron tolerance rhythms are modulated by season. The chronotoxic effect of a fixed dose (3.5 mg/kg, i.p.) of the drug was investigated with reference to both time of the day and year dependencies. Season‐related studies were performed on 560 male Swiss mice, 10 to 12 wks old, synchronized with L:D=12:12 for three weeks. During a 1 yr span (2005), four 24 h studies were performed with a single dosing time at 1, 7, 13, and 19 hours after light onset (HALO), respectively. Tolerance was assessed daily during a 40‐day span after acute ondansetron treatment. Both χ² test and cosinor methods were used to analyze the time series data. Statistically significant dosing time‐dependent changes were validated in both yearly and daily time scales. The 24 h mean survival rate peaked in spring (92%) compared to fall (72%), the 20% difference being statistically significant (χ² test with p<0.05 and cosinor with p<0.0001 for seasonal rhythm detection and with a peak time, Ø,=April 3±6.6 days). A 24 h rhythm was also detected in each of the seasonal time points. However, the curve pattern was monophasic in fall as well as spring. In fall, a large amplitude (A) circadian rhythm was detected that peaked at 19 HALO, while in the spring, a small circadian rhythm was detected that peaked at 1 HALO. The curve pattern was biphasic in summer (with large A) and in winter (with a small A). The existence of two peaks of equal magnitude in winter (100% survival rate) and in summer (100% and 90%) suggests the presence of both circadian and ultradian rhythms rather than an ultradian component of the 24 h period. The seasonal modulation of ondansetron circadian chronotolerance seems to involve several rhythm parameters: season‐related changes in the 24 h mean (M), amplitude (A), acrophase location (Ø), as well as bimodal curve patterns including the coexistence of rhythms with respectively 24 and 8 h periods in winter and summer. In conclusion, tolerance to ondansetron varies not only according to the 24 and 8 h periods but also according to seasons, which suggests the complexity of ondansetron toxicity rhythms. Seasonal modulation of ondansetron tolerance may also influence the strategies of chemo‐and chrono‐therapy, and it is therefore necessary to take it into account in clinical drug‐delivery protocols to minimize side effects of cytotoxic anticancer and antiemetic agents.     

Annual and circadian activity patterns of badgers (Meles meles) in Białowieża Primeval Forest (eastern Poland) compared with other Palaearctic populations

Aim The annual and circadian rhythms and duration of activity of Eurasian badger Meles meles (Linnaeus 1758) were studied in a low‐density population inhabiting the primeval woodland in the European temperate zone. Results were compared with available data from the literature on seasonal changes in body mass and winter inactivity of badgers from across the Palaearctic region. Location Field work was carried out in Bia?owie?a Primeval Forest, eastern Poland. Biogeographical variation was reviewed based on twenty‐three localities in the Palaearctic region (from Western Europe to Central Siberia). Methods Thirteen badgers were radio‐collared in 1997–2001. Their circadian activity was sampled by 24‐h sessions of continuous radio‐tracking with location taken at 15‐min intervals. Annual activity was studied by radio‐tracking and inspections of setts. Earthworm (badgers’ main food) biomass was estimated in four types of habitats throughout the year. Results Badgers were nocturnal with one long bout of activity. Their rhythms of diel activity differed between spring and autumn, and between adult and subadult individuals. On average, badgers emerged from setts at 19:00 hours and returned to them at 03:42 hours. The highest level of activity was recorded between 20:00 and 03:00 hours. Duration of daily activity was, on average, 8.2 h day^?1, but varied significantly between seasons. The seasonal changes were inversely related to the abundance of earthworms. Duration of activity also depended on daily temperature, especially in the cold season. In winter, badgers stayed inactive for an average of 96 days per year. In autumn, they built fat reserves and their body mass nearly doubled compared with the spring values. The literature review on annual cycle of activity and body mass changes in Eurasian badgers showed that fat storage and duration of winter sleep strongly depended on climate (best approximated by January mean temperature). In regions with warm climates, badgers were active year round and their body mass changed only slightly, while in regions with severe winters badgers increased their body mass twofold from spring to autumn, and stayed inactive for as long as 6 months per year. Main conclusion We propose that, in the temperate and boreal zones of the Palaearctic region, the ultimate determinant of biogeographical variation in badgers’ annual activity is the winter shortage of earthworms, which are the main component of badger diet.     

Seasonal Onset and Disappearance of Diurnal Rhythmicity in Melatonin Secretion in Female Reindeer

The reindeer (Rangifer tarandus tarandus) is a semidomesticatedholarctic ruminant subject to economic activity. Our researchwas carried out in Northern Finland, at latitude 69°10'N,where the daily light-dark rhythm has a polar pattern: constantdarkness starts on November 26th and lasts about 10 weeks, whilethe polar day of about 10 weeks starts on May 15th. We had previouslyfound distinct daily rhythms in reindeer melatonin secretionin autumn, winter and spring but not at all in summer. Herewe determine how the daily melatonin pattern develops afterthe period of polar day and how it disappears at the beginningof that period. Melatonin showed increased concentrations verysoon after the first sunset. Thereafter the daily pattern developedgradually and was fully developed around the autumn equinox.Its shape was asymmetric and the maximum amplitude occurrednear the end of the dark period. The disappearance of this dailypattern in spring was also gradual. The maximal concentrationsdepended on ambient illumination, especially the duration ofthe dark period. In spring the reindeer appeared to be moresensitive to light than in autumn. Additionally illuminationof the same magnitude suppressed serum melatonin levels moreeffectively before midnight than afterwards, which is in accordancewith the asymmetric secretion pattern. Melatonin secretion wasalways suppressed when the ambient illumination exceeded 1,0001x. The pattern of melatonin secretion in reindeer is differentfrom those described earlier and hence the reindeer may serveas a model for melatonin secretion at high latitudes. We suggestthat, in addition to the duration of the melatonin secretion,changes in amplitude are also of importance in the reindeer.     

Circadian rhythms of locomotor activity and temperature selection in sleepy lizards, <Emphasis Type="Italic">Tiliqua rugosa</Emphasis>

This study examined whether the daily rhythms of locomotor activity and behavioural thermoregulation that have previously been observed in Australian sleepy lizards (Tiliqua rugosa) under field conditions are true circadian rhythms that persist in constant darkness (DD) and whether these rhythms show similar characteristics. Lizards held on laboratory thermal gradients in the Australian spring under the prevailing 12-hour light : dark (LD) cycle for 14 days displayed robust daily rhythms of behavioural thermoregulation and locomotor activity. In the 13-day period of DD that followed LD, most lizards exhibited free-running circadian rhythms of locomotor activity and behavioural thermoregulation. The predominant activity pattern displayed in LD was unimodal and this was retained in DD. While mean levels of skin temperature and locomotor activity were found to decrease from LD to DD, activity duration remained unchanged. The present results demonstrate for the first time that this species’ daily rhythm of locomotor activity is an endogenous circadian rhythm. Our results also demonstrate a close correlation between the circadian activity and thermoregulatory rhythms in this species indicating that the two rhythms are controlled by the same master oscillator(s). Future examination of seasonal aspects of these rhythms, may, however, cause this hypothesis to be modified.     

Temporal Variations of Coagulation Factor VII Activity in Mice Are Influenced by Lighting Regime

It was recently reported that the circadian clock machinery controls plasma levels of factor (F) VII, the serine protease triggering blood coagulation. Here, by exploiting the mouse model, this study showed that variations of photoperiod (i.e., winter or summer conditions or simulated chronic jetlag conditions) have a strong impact on plasma FVII activity levels. Under conditions mimicking summer or winter photoperiods, FVII activity showed a clear 24 h rhythmicity. Interestingly, mean daily FVII activity levels were significantly reduced in mice exposed to summer photoperiods. Behavioral activity rhythms under both photoperiods were synchronized to LD cycles, and the amount of activity per 24 h was comparable. The authors also investigated the influence of chronic jetlag (CJL) on the FVII activity rhythms, which can be easily mimicked in mice through continuous abrupt shifts in the lighting schedule. The exposure of mice to simulated CJL of either consecutive westward or consecutive westward and eastward flights for 15 days did not abolish the behavioral activity rhythms but was associated with a period significantly different from 24 h. Intriguingly, both types of CJL exerted a strong influence on FVII activity rhythms, which were virtually suppressed. Moreover, the mean daily FVII activity was significantly lower in the CJL than in the winter photoperiod condition. Taken together, these findings in mice provide novel insights into the modulation of FVII activity levels, which might have implications for human pathophysiology.     

Temporal variations of coagulation factor VII activity in mice are influenced by lighting regime

It was recently reported that the circadian clock machinery controls plasma levels of factor (F) VII, the serine protease triggering blood coagulation. Here, by exploiting the mouse model, this study showed that variations of photoperiod (i.e., winter or summer conditions or simulated chronic jetlag conditions) have a strong impact on plasma FVII activity levels. Under conditions mimicking summer or winter photoperiods, FVII activity showed a clear 24 h rhythmicity. Interestingly, mean daily FVII activity levels were significantly reduced in mice exposed to summer photoperiods. Behavioral activity rhythms under both photoperiods were synchronized to LD cycles, and the amount of activity per 24 h was comparable. The authors also investigated the influence of chronic jetlag (CJL) on the FVII activity rhythms, which can be easily mimicked in mice through continuous abrupt shifts in the lighting schedule. The exposure of mice to simulated CJL of either consecutive westward or consecutive westward and eastward flights for 15 days did not abolish the behavioral activity rhythms but was associated with a period significantly different from 24 h. Intriguingly, both types of CJL exerted a strong influence on FVII activity rhythms, which were virtually suppressed. Moreover, the mean daily FVII activity was significantly lower in the CJL than in the winter photoperiod condition. Taken together, these findings in mice provide novel insights into the modulation of FVII activity levels, which might have implications for human pathophysiology.     

Circannual rhythms in the blood picture of laboratory rats

Circannual rhythms of the erythrocyte, total leucocyte, absolute segmented neutrophil and lymphocyte counts in laboratory Wistar rats were found. The highest mean counts occurred in autumn and at the begining of winter. The lowest counts werte recorded in spring and at the begining of summer. A similar circannual rhythm of absolute eosinophil counts in females was also found, but it was not present in males. Circannual rhythms of the relative lymphocyte, segmented neutrophil and eosinophil were not found. The course of seasonal variations in erythrocyte, total leucocyte, absolute segmented neutrophil and lymphocyte counts of males was similar to those of females.     

Seasonal variation in blood concentrations of interleukin-6, adrenocorticotrophic hormone,metabolites of catecholamine and cortisol in healthy volunteers

We investigated seasonal changes in blood concentrations of interleukin-6 (IL-6), adrenocorticotrophic hormone (ACTH), metabolites of catecholamine (VMA, HVA, and 5-HIAA) and cortisol in humans. Eight volunteers were investigated at four times during the year (February, May, August and October) at latitude 35° N. The mean ambient temperature at the collection periods was higher in the order of summer > autumn ≈ spring > winter. Changes in mood were also monitored by a profile of mood states (POMS) questionnaire. The concentration of IL-6 was significantly higher in winter and summer than in spring and autumn. The concentrations of ACTH, HVA and VMA were significantly higher in summer. No seasonal variation was detected in cortisol. There were significant differences among the seasons in subscale tension and anger in the POMS questionnaire; the tension subscale showed significant differences between spring and autumn, with a higher score in spring. The results demonstrate that Il-6, ACTH, HVA and VMA exhibit statistically significant seasonal rhythms, which might have important diagnostic and therapeutic implications.     

Seasonal variation of activity patterns in roe deer in a temperate forested area

We investigated the activity patterns of a European roe deer (Capreolus capreolus) population living in a forested Apennine area in central Italy, in order to shed light on the environmental and biological factors that were expected to account for the observed activity patterns on daily and yearly bases. Daily and seasonal activity patterns of 31 radio-collared roe deer were assessed through sessions of radio tracking for a total period of 18 consecutive months. Roe deer showed bimodal activity patterns throughout the year, with the two highest peaks of activity recorded at dawn and dusk. Activity patterns of males and females differed during the territorial period (from early spring to late summer), whereas they did not during the nonterritorial period. Most likely, behavioral thermoregulation can be held responsible for variation of daily activity patterns in different seasons. In winter, for instance, activity during the dawn period was significantly higher than in other seasons and daylight activity was significantly higher than at night. Nocturnal activity was highest in summer and lowest in winter. During the hunting season, moreover, roe deer showed lower activity levels than during the rest of the year. The prediction that roe deer would show lower activity levels during full moon nights, when the predation risk was assumed to be higher, was not confirmed by our data. Activity rhythms in roe deer were thus subjected to both endogenous and environmental factors, the latter working as exogenous synchronization cues. Accordingly, in changing environmental and ecological conditions, a circadian cycle of activity could be seen as the result of complex interactions among daily behavioral rhythm, digestive physiology, and external modifying factors.