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This study aimed to verify the daily variation in the chromatic visual sensitivity of healthy subjects. The study included 35 male adults, aged between 20 and 40 years old (M = 24.97; SD = 4.9). The evaluation of color perception was made through the Cambridge Colour Test, using the Trivector and Ellipse tests. The Pittsburgh Sleep Quality Index, the Sleep Diary, and the Karolinska Sleepiness Scale were used to assess possible influences of circadian rhythmicity. Significant differences were found for the protan confusion axes at 8 am (Z = 2.9; p = 0.012) and at 8 pm (Z = 2.8; p = 0.01), and deutan at 8 am (Z = 2.6; p = 0.028) and at 8 pm (Z = 3.5; p = 0.001), and for the A1 ellipses areas at 8 am (Z = 2.5; p = 0.037) and at 8 pm (Z = 2.4; p = 0.018), and A3 at 8 am (Z = 2.1; p = 0.039) and at 8 pm (Z = 3.6; p = 0.001). Thus, chromatic sensitivity can be characterized by an inverted U-shaped curve, with peak sensitivity in the morning and evening, and attenuation in the afternoon. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the daily total locomotor activity in captive Chrysocyon brachyurus. Three maned wolves were housed individually under natural light–dark cycle and environmental conditions. In each animal, locomotor activity was monitoored for 30 days by means of an activity data logger (Actiwatch Cambridge©Neurotechnology, Cambridge, UK), applied on a neck collar. Locomotor activity was evaluated by visual inspection of actograms. The average amount of activity during light and dark phases and Cosine 20 Peak were calculated using Actiwatc Activity Analysis 5.06. Subject A was more active during the light phase, and subjects B and C were more active during the dark phase. The single cosinor method applied on the amount of activity recorded every hour showed a daily rhythm of locomotor activity only in subject B (2 years old). Acrophase was observed between 03:20 and 07:30, and robustness had a value between 37.00% and 63.40%. Only one subject due to their early withdrawal from its natural habitat, developed a manifest anthropic dependence, with a marked adaptation to the habitat of captivity presenting an anthropophilic behavior. This study would help to define more appropriate management and conservation strategies for this emblematic mammal of South America. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the daily variations of urinary excretion of the main electrolytes in Equus caballus and Bos taurus maintained under natural photoperiod. Animals were housed in individual indoor stalls under natural conditions. Urine and blood samples were taken from all the subjects every 4 h for 24 h period and were analyzed to assess the creatinine, calcium, phosphorus, magnesium, and chloride concentration. The fractional excretions of Na (%CrNa), K (%CrK), Cl (%CrCl), P (%CrP), Ca (%CrCa), and Mg (%CrMg) were calculated. Daily oscillations with nighttime acrophases of %CrNa, %CrK, and %CrCl are observed in horse; the acrophases of the parameters which resulted periodic in cow, including %CrNa, %CrCa, and %CrMg, are verified during the light phase. This study brings a contribution to the knowledge of the periodic phenomenon of the urinary excretion in the equine and bovine species. The results suggest that horse and cow are characterized by different circadian patterns for renal fractional clearance and that in these species, in addition to the external circadian stimuli, the renal excretion rhythms are also controlled by a self-sustained intrinsic renal clock that contribute to define the temporal patterns (daytime and nighttime). [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the influence of different photoperiod schedules on daily total locomotor activity in cat. Four male cats (4 ± 0.3 kg) were housed individually under controlled temperature during the study and were subjected to four different artificial lighting regimes including 12L:12D (light on at 08:00, light off at 20:00), 12D:12L (light on at 20:00, light off at 08:00), 24L:0D (light on for all experimental period), 0L:24D (constant darkness). The application of the statistical analysis of cosinor indicated the existence of a significant daily rhythm (P < 0.05). In particular, in 12L:12D conditions, the cats were more active during the dark phase compared to the light phase, with a range of variation between 23:30 and 24:30 h. During the 12D:12L cycle, all cats changed their locomotor activity rhythm, so that it coincided with the new phase of the photoperiod. The resynchronization to a new LD cycle was quick. Endogenous rhythms were manifested in all cats with different clarity when subjected to 24L:0D cycles. When the cats were exposed to constant darkness, the endogenous periodicity was not observed. These results suggest the existence of an endogenous circadian oscillator that controls the expression of locomotor activity rhythms in the cat. [ABSTRACT FROM AUTHOR]

Many ungulates are reported to use natural or artificial licks with seasonal patterns around the world. From December 2016 to August 2017, we used infrared camera to record the use of artificial licks in wild sika deer (Cervus nippon) in Zhejiang Qingliangfeng National Nature Reserve, China. We explored the daily rhythm, seasonal pattern and sex difference in lick utilization. In total, 12,043 videos and 22,901 pictures were collected. Our results showed that: (1) the lick visiting frequency was higher at night than that during daytime; (2) the difference in lick visiting frequency between females and males disappeared after taking into account of sex ratio; (3) the lick duration peaked in April during a year. These findings suggested that there were clear daily rhythm and seasonal pattern of lick use in sika deer. Seasonal change in lick use intensity was consistent with our prediction. These variations in lick use might be driven by both the physiological needs of the mineral elements in different life stages and the seasonal changes in climate and food. The reserve management authority should pay more attention to the supplement of licks in spring and summer to fulfill animal's physiological needs. [ABSTRACT FROM AUTHOR]

The impact of L-serine on the daily rhythms of growth hormone (GH) and corticosterone remains unknown. We explored whether the daily rhythms of these hormones were affected by L-serine supplementation as well as the supplementation time. The results showed that plasma GH concentration at Zeitgeber time (ZT)4 and 8 were significantly increased by L-serine supplementation at ZT22, while the diurnal rhythms peaks of plasma corticosterone at ZT12 were suppressed by L-serine supplementation at ZT10. After the supplementation was stopped, the effects of L-serine on the diurnal rhythms of plasma GH and corticosterone lasted for 2 days then they were fading on day 4. L-serine concentrations in plasma and hypothalamus after supplementation at ZT22 was lower than those after supplementation at ZT10. In conclusion, L-serine modulates the daily rhythms of GH and corticosterone depending on its supplementation time. The modulation effect might be association with the daily rhythms of L-serine metabolism. [ABSTRACT FROM AUTHOR]

The aim of the present study was to monitor the daily rhythm of rectal and cutaneous temperatures together with the changes in the serum levels of mitochondrial uncoupling protein 1 (UCP1) in equine and goat species. On five gelding horses and five female goat rectal and cutaneous temperatures were recorded at 4 h intervals for a 48 h period. At the same time points blood samples were collected from each animal. Daily rhythms of rectal and cutaneous temperatures were observed in both species, in both day of monitoring. Mesor value of rectal temperature was statistically higher of about 4 °C than cutaneous temperature, and acrophase was postponed of about 2 h in both day of monitoring and in both species. UCP1 did not show daily rhythmicity in horses and goats. We can speculate that the thermogenesis due to thermal system is auxiliary to keeping the body temperature daily rhythm. [ABSTRACT FROM PUBLISHER]

This study evaluates the pattern of plasma melatonin during the trough and the peak of its daily rhythm. Blood samples from 8 ewes were collected every 3 h for a 48-h period. On the third day, blood samples were collected from 10:00 to 13:00 (trough) and from 20:00 to 23:00 (peak) every 20 min. Our results showed a robust daily rhythm of melatonin in both days of monitoring, with nocturnal acrophase. During the trough, a significant decrease was observed starting from the 10:40 with a progressive decrease about every 40 min. During the peak of the plasma melatonin daily rhythm, an increase was observed starting from the 20:40 with a progressive increase about every 40 min. These data could be taken in consideration to monitor the plasma melatonin variations during the 24 h, and for the administration of melatonin for breeding in ewes. [ABSTRACT FROM AUTHOR]

In order to investigate the potential causal link between the rhythm of activity and body temperature, we simultaneously recorded rectal temperature and total locomotor activity in five clinically healthy female rabbits (blue Vienna breed), 12 week old and mean body weight 2.7 ± 0.3. Animals were housed in individual cages (90 × 50 × 35 cm) under natural 12/12 light/dark cycle. Total locomotor activity was monitored for 15 days by an activity data logger. On day 1, 5, 10, and 15 rectal temperature was recorded every 2 h for a 24-h period. Application of single cosinor method showed a nocturnal daily rhythm of rectal temperature with a range of oscillation of about 1 °C, acrophase after dusk and low robustness value. The daily rhythm of locomotor activity showed its acrophase in the middle of the scotophase and a high robustness value. This information improves the knowledge available on the circadian biology of rabbits useful in the evaluation of physiology of this species. [ABSTRACT FROM PUBLISHER]

Keeping and management of horses can induce changes to instinctive and innate behavioural patterns. We investigated the effect of five different management conditions in five groups of horses. All groups were housed in individual boxes under natural environmental and lighting conditions. They were fed three times a day (07:00, 12:30 and 20:00) and had free access to water. Group A was fed with 8 kg/capo/die of hay divided in the three meals. Group B was fed with 8 kg/capo/die of an unifeed divided in the three meals. Group C was fed with unifeed at 07:00 and 12:30 and with hay at 20:00. They were kept in wood-bedded boxes. Groups D and E were fed with unifeed at 07:00 and 12:30, respectively, and in the other, two meals received hay. They were kept in straw-bedded boxes. Our results showed a daily rhythm of total locomotor activity in all groups, influenced by management conditions. Group A engaged in meal patterns similar to those seen in grazing animals. Groups B and C showed the highest MESOR values due to a high searching behaviour. Group C showed a nocturnal acrophase contrary to the other groups. Groups D and E showed a total locomotor activity pattern similar to that observed in Group A probably due to an increase in straw-bedding consuming. The reduction of fibre in diet has an impact on physiology and behaviour of horses. The valuation of diet and in bedding provided to horses kept in box is useful to guarantee the maintenance of the physiological daily rhythm of total locomotor activity. [ABSTRACT FROM PUBLISHER]

To investigate the daily rhythm of rectal and vaginal temperature, we used six mongrel dogs with a mean body weight of 15±3 kg, aged between 2 and 3 years old. Rectal and vaginal temperatures were recorded every 3 h over 48-h period during three different lighting regimes: natural light/dark (L/D) cycle (sunrise 06:25, sunset 17:05), constant light (L/L) and constant darkness (D/D). A daily rhythm of rectal temperature was observed in both days of monitoring in all experimental conditions. Vaginal temperature showed a daily rhythmicity in L/D and D/D cycle. During the L/L cycle, daily rhythm was disrupted. Rhythmic parameters (MESOR, amplitude, acrophase and robustness) did not change between the different photoperiod and the site of temperature collection. In conclusion, the monitoring of vaginal temperature can be considered a valid alternative to the monitoring of body temperature as well as rectal temperature under natural lighting conditions in canine medicine. [ABSTRACT FROM PUBLISHER]

The aim of this study was to characterize cats and dogs’ locomotor activity patterns in relation to housing conditions and owner interaction. Five adult cats and five adult dogs belonging to ten different owners were enrolled in the study. Animals were housed in apartments having daily access to the garden. Total locomotor activity (TLA) was recorded for one week by means of Actiwatch-Mini®. The amount of activity was higher during the photophase than during the scotophase both in cats and dogs. Cats showed no daily rhythmicity of TLA, while dogs exhibited a daily rhythmicity with diurnal acrophase and high robustness values. We can claim that owner’s presence influenced TLA of two studied species in different way: dogs showed higher amount of TLA and robustness, while cats lost their rhythmicity. [ABSTRACT FROM AUTHOR]

The study aimed to test differences in immune ability and clock gene expression between intact fish and ophthalmectomized yellowtail clownfish exposed to light-emitting diodes (LEDs). Clock genes (Period 2, Per2; Cryptochrome 1, Cry1) and melatonin receptor 1 mRNA and protein expression in all wavelengths groups were significantly lower in ophthalmectomized fish than in intact fish, but ophthalmectomized fish exposed to green and blue LEDs showed expression levels similar to intact fish. Furthermore, indicators of immune activity (immunoglobulin M; IgM mRNA and protein expression and lysozyme activity) were significantly higher in ophthalmectomized fish exposed to green and blue LEDs than other groups of ophthalmectomized fish. Also, plasma H2O2levels in ophthalmectomized fish exposed to green and blue LEDs showed their levels similar to intact fish. These results suggest that short wavelengths affect the daily rhythms of fish and enhance the immune ability, even in the absence of an eye. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the influence of housing conditions on daily rhythm of total locomotor activity in dogs. Seven clinically healthy dogs (Canis familiaris) were used and divided into two groups: Group A lived with its owner in indoor environment, Group B housed in individual box of 140 × 200 cm. Each dog was equipped by means of collar on the neck with an actigraphy-based data logger (Actiwatch-Mini®, Cambridge Neurotechnology Ltd, UK), that record a digitally integrated measure of motor activity. In both groups, a daily rhythm of locomotor activity was observed. In Group A, acrophase and robustness changed during the 10 days of monitoring. In Group B, no changes were observed, and robustness was lower than Group A. Our findings underline the high influence of human presence and care on the amount of activity and on daily rhythm in companion dogs. [ABSTRACT FROM PUBLISHER]

The aim of the present study was to investigate the influence of three-time feeding on insulin daily rhythm in horses. At this purpose, five clinically healthy Italian saddle horses were housed under natural photoperiod (L/D) followed by constant darkness (D/D). Horses were fed three times a day (6:00; 12:00; 18:00) with hay and a mix of cereals. Blood samples were collected every 3 h over 48-h period (24 h during L/D and 24 h during D/D). On each serum sample insulin concentration was assessed. Two-way for repeated measures analysis of variance (ANOVA) was applied to investigate statistically differences due to time of day and experimental conditions. Cosinor rhythmometry was applied to investigate daily rhythmicity in the two experimental periods. Our results showed a significant effect of time of day and experimental conditions on serum insulin concentrations. Daily rhythmicity of insulin serum concentrations was observed during L/D and D/D. Statistically differences in MESOR (Midline-Estimating Statistic of Rhythm), amplitude and acrophases were observed between L/D and D/D. MESOR and amplitude statistically decreased in D/D respect to L/D, and acrophase was postponed in L/D respect to D/D. Robustness of rhythm did not change between the two experimental period. In conclusion, we can hypothesised that the daily rhythm of insulin in horses is endogenously generated; and that during the routine management of the stabled horses providing feed three times a day favourite the physiological secretion of insulin in this species. [ABSTRACT FROM PUBLISHER]

The aim of the present study was to show the presence of circadian rhythm of muscle strength under a standardised protocol with controlled parameters to support suitable observation of variability during the day. Eight male volunteers were evaluated once a week for 6 weeks at six different times. Rectal temperature, peak torque (PT), maximum work and the average power of the flexor and extensor knee muscles in the isokinetic mode, as well as of PT in maximum voluntary isometric contraction of knee extensors at 60° knee flexion, were measured. The present study showed rhythms with a period of 24 hours in some indices of muscle strength performance at both speeds of movement and muscle groups. To our knowledge, this is the first study that has shown the presence of circadian rhythm in all speeds of movement and muscle groups tested under strict standardised protocol. [ABSTRACT FROM AUTHOR]

To establish the accuracy of the auricular temperature assessment in alternative to the rectal temperature determination in canine medicine, we compared the rhythmicity of rectal temperature with the rhythmicity of auricular temperature in healthy dogs. Eight Rottweilers, eight Beagles and eight Teckels were housed in individual pens under natural photoperiod and environmental conditions. Rectal and auricular temperatures were recorded every 3 hours over a 48 hour period. A significant effect of time of day, breed and side of temperature collection on the temperature values was observed. Strong similarity between rectal and auricular temperature trend and daily rhythmicity was observed. In dogs, it could be possible to utilize auricular temperature for estimating body temperature, taking into consideration that it is 1.3°C lower than rectal temperature. [ABSTRACT FROM AUTHOR]

This article reviews the literature on the daily rhythm in horses. Many physiological processes have been studied in horses to investigate their daily rhythmicity. In horses many rhythms are driven by an endogenous pacemaker, some of them endogenously generated, others influenced by external stimuli. It then addresses the influence of maturation and ageing, physical exercise and jet lag on these rhythms. The study of daily rhythms in horses is of considerable importance in all aspects of horse management to maintain the natural physiological behaviours of this species, necessary to guarantee the good welfare in breeding and athlete horses. Chronophysiology in horses also has clinical implications, it can influence disease occurrence, diagnostic tests and the effect of medical treatments. [ABSTRACT FROM AUTHOR]

The locomotor circadian rhythm has been much studied in recent decades, using automated apparatus for the collection of circadian locomotor data. Although this method is convenient, some important characteristics of activity are probably lost. Here, we have observed and recorded manually the locomotor circadian rhythm in adults of Drosophila melanogaster. This has enabled locomotor characteristics to be recorded, but it is a very labor-intensive process. Results showed that: (1) The locomotor behavior in Drosophila melanogaster was composed of strong and weak activities, both of which exhibited a bimodal pattern with morning and evening peaks. (2) The strong activity played a leading role during lights-on and lights-off, while the weak activity occurred mainly around the middle of the dark period. (3) Females displayed higher activity levels during the evening peak and daytime, while males did so in the night and during the morning peak. [ABSTRACT FROM AUTHOR]

The goal of the present study was to investigate the influence of feeding and fasting on daily rhythm of serum creatinine in dogs. Blood samples from 10 purebred Beagle dogs were collected at 4-h intervals for 48 h (starting at 07:00 on day 1 and finishing at 03:00 on day 2). Statistical analysis of the data was performed by one-way repeated-measures analysis of variance (ANOVA) and by single cosinor method. Cosinor analysis identified the periodic parameters and their acrophases during the two days of monitoring. On each day, there was a highly significant effect of time in all dogs, with P values <0.05. Our results indicate the existence of a temporal relationship between serum creatinine concentration and feeding-asting cycles and suggest that food intake is a physiological trigger for the synthesis and secretion of creatinine. [ABSTRACT FROM AUTHOR]

We described the daily rhythms of parameters involved in melatonin production in the pineal of viscacha. Norepinephrine showed the highest levels at night. A peak in β1-adrenoceptor mRNA was observed at the end of the light phase. Serotonin exhibited higher values during the light period. AA-NAT mRNA showed the highest expression at Zeitgeber time 0 (ZT0), reaching a minimum at night. AA-NAT activity and melatonin content exhibited a nocturnal peak at ZT16, a lower diurnal increase during the light period and minimal level at ZT8. HIOMT activity showed a peak at ZT16. The daily pattern in norepinephrine content was similar to that of AA-NAT activity and melatonin levels. Our data suggest that the melatonin synthesis in viscacha might be activated via adrenergic induction; the differences observed in the daily rhythms of AA-NAT activity and its mRNA suggest that post-transcriptional mechanisms may be involved, and other Zeitgeber and other mechanisms might also control melatonin production. [ABSTRACT FROM AUTHOR]

Daily rhythms are described in almost every variable that can be measured, including suicide rate. The present study aims to find if circadian rhythm exist in suicidal poisoning and completed suicide due to poisoning in central Nepal. The study included all the attempted suicide cases admitted in Patan Hospital and all the completed suicide cases by poisoning reported to Kathmandu District Police during March 2002 to April 2003. The time was grouped into 24 increments of 1 hour. The data were analysed by Kolmogorov-Smirnov test and cosinor analysis. The circadian rhythm of attempted suicide by deliberate self poisoning exhibits a peak at 18:00 h, whereas no circadian rhythm is seen in completed suicides by poisoning although it is bimodal in distribution (6:00-12:00 and 15:00-20:00) with peaks at 7:00 and 18:00 h. [ABSTRACT FROM AUTHOR]