Sleep pattern in the dromedary camel: a behavioral and polysomnography study

Study Objectives

To investigate sleep patterns in the camel by combining behavioral and polysomnography (PSG) methods.

Methods

A noninvasive PSG study was conducted over four nights on four animals. Additionally, video recordings were used to monitor the sleep behaviors associated with different vigilance states.

Results

During the night, short periods of sporadic sleep-like behavior corresponding to a specific posture, sternal recumbency (SR) with the head lying down on the ground, were observed. The PSG results showed rapid shifts between five vigilance states, including wakefulness, drowsiness, rapid eye movement (REM) sleep, non-REM (NREM) sleep, and rumination. The camels typically slept only 1.7 hours per night, subdivided into 0.5 hours of REM sleep and 1.2 hours of NREM sleep. Camels spent most of the night being awake (2.3 hours), ruminating (2.4 hours), or drowsing (1.9 hours). Various combinations of transitions between the different vigilance states were observed, with a notable transition into REM sleep directly from drowsiness (9%) or wakefulness (4%). Behavioral postures were found to correlate with PSG vigilance states, thereby allowing a reliable prediction of the sleep stage based on SR and the head position (erected, motionless, or lying down on the ground). Notably, 100% of REM sleep occurred during the Head Lying Down-SR posture.

Conclusions

The camel is a diurnal species with a polyphasic sleep pattern at night. The best correlation between PSG and ethogram data indicates that sleep duration can be predicted by the behavioral method, provided that drowsiness is considered a part of sleep.

Seasonal variations in locomotor activity rhythm and diurnal activity in the dromedary camel (Camelus dromedarius) under mesic semi-natural conditions

The dromedary camel (Camelus dromedarius) is a large ungulate that copes well with the xeric environment of the desert. Its peculiar adaptation to heat and dehydration is well-known. However, its behavior and general activity is far from being completely understood. The present study was carried out to investigate the ecological effect of the various seasons on the locomotor activity (LA) rhythm and diurnal activity of this species. Six adult female camels were maintained under mesic semi-natural conditions of the environment during four periods of 10 days in each season: autumn, winter, spring and summer. In addition, three female camels were used to test the effect of rain on the LA rhythm during a period of 18 days during the winter. The animal's LA was recorded using the locomotion scoring method. Camels displayed a clear 24.0h LA rhythm throughout the four seasons. Activity was intense during Day-time (6-22 fold higher in comparison to night) and dropped or completely disappeared during nighttime. Mean daytime total activity was significantly higher in the summer as compared to winter. Regardless of the season, the active phase in camels coincided with the time of the photophase and thermophase. Furthermore, the daily duration of the time spent active was directly correlated to the seasonal changes of photoperiod. The diurnal activity remained unchanged over the four seasons. For each season, the start and the end of the active phase were synchronized with the onset of sunrise and sunset. At these time periods, temperature remained incredibly stable with a change ranging from 0.002 to 0.210°C; whereas, changes of light intensity were greater and faster with a change from 0.1 to 600 lux representing a variation of 3215-7192 fold in just 25-29 min. Rainfall affected the pattern of the LA rhythm with occurrence of abnormal nocturnal activity during nighttime disturbing nocturnal rest and sleep. Here we show that the dromedary camel exhibits significant seasonal changes of its activity within daylight hours. However, the diurnal pattern remains unchanged regardless of the season; whereas, abnormal nocturnal activity is observed during periods of rain. The activity onset and offset in this species seems to be primarily driven by the changes in light intensity at dusk and dawn.

Melatonin rhythm and other outputs of the master circadian clock in the desert goat (Capra hircus) are entrained by daily cycles of ambient temperature

In desert areas, mammals such as camel and goat are exposed to harsh environmental conditions. The ambient temperature (Ta) cycles have been shown to entrain the circadian clock in the camel. In the present work, we assumed that, in the goat living in a desert biotope, Ta cycles would have the same synchronizing effect on the central clock. Therefore, the effects of Ta cycles on body temperature (Tb), locomotor activity (LA) and melatonin (Mel) rhythms as outputs of the master circadian clock have been studied. The study was performed on bucks kept first under constant conditions of total darkness (DD) and constant Ta, then maintained under DD conditions but exposed to Ta cycles with heat period during subjective day and cold period during subjective night. Finally, the Ta cycles were reversed with highest temperatures during the subjective night and the lowest temperatures during the subjective day. Under constant conditions, the circadian rhythms of Tb and LA were free running with an endogenous period of 25.3 and 25.0 hours, respectively. Ta cycles entrained the rhythms of Tb and LA to a period of exactly 24.0 hours; while when reversed, the Ta cycles led to an inversion of Tb and LA rhythms. Similarly, Ta cycles were also able to entrain Mel rhythm, by adjusting its secretion to the cooling phase before and after Ta cycles inversion. All together, these results show that the Ta cycles entrain the master circadian clock in the goat.

Dataset concerning haematological and biochemical parameters changes in show jumping horses subjected to exercise and plasmapheresis session

This article presents data on the effect of plasmapheresis on clinical, haematological and biochemical parameters in horses following exercise and after a plasmapheresis session. This blood filtration technique was realised on six jumping horses (plasmapheresis group) that underwent three consecutive days of graded physical exercise. The control group (n = 6) went through the same exercise but was not subjected to the plasmapheresis session. Blood was sampled before and after each exercise, also at the beginning and the end of plasmapheresis session. The presented data was obtained by measuring clinical and haemato-biochemical parameters in both groups. The heart and respiratory rates and rectal temperature were recorded. In addition, the number of red blood and white cells, platelets also of lymphocytes, monocytes, eosinophils and granulocytes were counted. Other haematological parameters including, hemoglobin concentration, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration were determined. Concerning the biochemical parameters, the concentrations of albumin, globulin, total protein, glucose, alkaline phosphatase, aspartate aminotransferase, gamma glutamyl transferase, total bilirubin, lactate, creatinine kinase, urea, creatinine, calcium, sodium and potassium were measured. All parameters data were analyzed by a two-way repeated measures analysis of variance followed by Holm-Sidak post-hoc procedure to evaluate the effect of plasmapheresis and time. This paper contains data related to and supporting research articles currently published entitled "Plasmapheresis effect on haematological and biochemical parameters in athletic horses subjected to exercise" (Daden et al., 2019) [1].

Plasmapheresis Effect on Hematological and Biochemical Parameters in Athletic Horses Subjected to Exercise

To evaluate the effect of plasmapheresis on clinical, hematological, and biochemical parameters after exercise, a plasmapheresis session was realized on six jumping horses (plasmapheresis group) that underwent three consecutive days of physical graded exercise. The control group (n = 6) went through the same exercise but not subjected to the plasmapheresis session. Seventeen milliliters of plasma/kg of body weight was harvested from each horse. The procedure was well tolerated by the horses. The plasmapheresis leads to a significant increase of the hemoglobin, hematocrit, red blood cell, white blood cell, and lymphocytes counts. Plasmapheresis induced a very significant decrease (P < .001) of albumin and globulin levels and of total protein, which were reestablished 24 hours later. Plasmapheresis also generated a very significant increase (P < .001) in sodium levels and a significant decline of potassium (P < .05) and calcium (P < .01) levels. Several other biochemical variables remained unchanged. Results also showed that, after a significant rise of lactate, aspartate aminotransferase, and creatine kinase levels which are subsequent to the exercise, the plasmapheresis session induced a very significant continuous decrease (P < .001) of these parameters. The present work has demonstrated that the plasmapheresis is able to modify the physiology after exercise and to affect both the hematology and the biochemistry of the blood hematobiochemical parameters in horses subjected to physical exercise.

The dromedary camel displays annual variation in hypothalamic kisspeptin and Arg-Phe-amide-related peptide-3 according to sex, season, and breeding activity

The dromedary camel (Camelus dromedarius) is a desert mammal whose cycles in reproductive activity ensure that the offspring's birth and weaning coincide with periods of abundant food resources and favorable climate conditions. In this study, we assessed whether kisspeptin (Kp) and arginine-phenylalanine (RF)-amide related peptide-3 (RFRP-3), two hypothalamic peptides known to regulate the mammalian hypothalamo-pituitary gonadal axis, may be involved in the seasonal control of camel's reproduction. Using specific antibodies and riboprobes, we found that Kp neurons are present in the preoptic area (POA), suprachiasmatic (SCN), and arcuate (ARC) nuclei, and that RFRP-3 neurons are present in the paraventricular (PVN), dorsomedial (DMH), and ventromedial (VMH) hypothalamic nuclei. Kp fibers are found in various hypothalamic areas, notably the POA, SCN, PVN, DMH, VMH, supraoptic nucleus, and the ventral and dorsal premammillary nucleus. RFRP-3 fibers are found in the POA, SCN, PVN, DMH, VMH, and ARC. POA and ARC Kp neurons and DMH RFRP-3 neurons display sexual dimorphism with more neurons in female than in male. Both neuronal populations display opposed seasonal variations with more Kp neurons and less RFRP-3 neurons during the breeding (December-January) than the nonbreeding (July-August) season. This study is the first describing Kp and RFRP-3 in the camel's brain with, during the winter period lower RFRP-3 expression and higher Kp expression possibly responsible for the HPG axis activation. Altogether, our data indicate the involvement of both Kp and RFRP-3 in the seasonal control of the dromedary camel's breeding activity.

Smartphone and a freely available application as a new tool to record locomotor activity rhythm in large mammals and humans

Daily pattern of locomotor activity (LA), one of the most studied rhythms in humans and rodents, has not been widely investigated in large mammals. This is partly due to the high cost and breakability of used automatic devices. Since last decade, smartphones are becoming ubiquitous. Meanwhile, several applications detecting activity by using internal sensors were made available. In this study, we assumed that this device could be a cheaper and easier way to measure the LA rhythm in humans and large mammals, like camel and goat. A smartphone application (Nokia Mate Health), normally used to quantify physical activities in humans, was chosen for the study. To validate the rhythm data obtained from the smartphone, LA rhythm was simultaneously recorded using an automatic device, the Actiwatch-Mini®. Results showed that the smartphone provided a clear and significant daily rhythm of LA. The visual assessment of the superimposed LA rhythm's curves in all three species showed that the smartphone application displayed similar rhythms as those recorded by the Actiwatch-Mini. Highly significant positive correlation (p≤ 0.0001) exists between the two recording rhythms. The daily periods were both the same at 24.0 h. Acrophases were also significantly similar and occurring around mid-day: 11:40 ± 0.35 h vs 11:41 ± 0.35 h for the camel, 11:25 ± 0.19 h vs 11:37 ± 0.25 h for the goat and 13:04 ± 0.11 h vs 13:51 ± 0.28 h for humans using smartphone and Actiwatch, respectively. The related mesor and amplitude were also close between the two recording devices. Results indicate clearly that using smartphones constitutes a reliable cheap tool to study LA rhythm for chronobiology studies, especially in laboratories facing lack of funding.

Validation of locomotion scoring as a new and inexpensive technique to record circadian locomotor activity in large mammals

Background

The locomotor activity (LA) rhythm, widely studied in rodents, has not been fully investigated in large mammals. This is due to the high cost and the brittleness of the required devices. Alternatively, the locomotion scoring method (SM), consisting of attribution of a score to various levels of activity would be a consistent method to assess the circadian LA rhythm in such species.

New method

To test this, a SM with a score ranging from 0 to 5 has been developed and used in two domestic large mammals, the camel and the goat. One minute interval scoring was performed using visual screening and monitoring of infra-red camera recording videos and carried out by two evaluators.

Results

The SM provides a clear daily LA rhythm that has been validated using an automate device, the Actiwatch-Mini. The obtained curves and actograms were indeed highly similar to those acquired from the Actiwatch-Mini. Moreover, there were no statistical differences in the period and acrophase. The period was exactly of 24.0h and the acrophases occurred at 12h05 ± 00h03 and 12h14 ± 00h07 for the camel and at 13h13 ± 00h09 and 12h57 ± 00h09 for the goat using SM and Actiwatch-Mini respectively.

Comparison with existing methods

Compared to the automatic system, the SM is inexpensive and has the advantage of describing all types of performed movements.

Conclusions

The new developed SM is highly reliable and sufficiently accurate to assess conveniently the LA rhythm and specific behaviors in large mammals. This opens new perspectives to study chronobiology in animal models of desert, tropical and equatorial zones.

The Suprachiasmatic Nucleus of the Dromedary Camel (Camelus dromedarius): Cytoarchitecture and Neurochemical Anatomy

In mammals, biological rhythms are driven by a master circadian clock located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Recently, we have demonstrated that in the camel, the daily cycle of environmental temperature is able to entrain the master clock. This raises several questions about the structure and function of the SCN in this species. The current work is the first neuroanatomical investigation of the camel SCN. We carried out a cartography and cytoarchitectural study of the nucleus and then studied its cell types and chemical neuroanatomy. Relevant neuropeptides involved in the circadian system were investigated, including arginine-vasopressin (AVP), vasoactive intestinal polypeptide (VIP), met-enkephalin (Met-Enk), neuropeptide Y (NPY), as well as oxytocin (OT). The neurotransmitter serotonin (5-HT) and the enzymes tyrosine hydroxylase (TH) and aromatic L-amino acid decarboxylase (AADC) were also studied. The camel SCN is a large and elongated nucleus, extending rostrocaudally for 9.55 ± 0.10 mm. Based on histological and immunofluorescence findings, we subdivided the camel SCN into rostral/preoptic (rSCN), middle/main body (mSCN) and caudal/retrochiasmatic (cSCN) divisions. Among mammals, the rSCN is unusual and appears as an assembly of neurons that protrudes from the main mass of the hypothalamus. The mSCN exhibits the triangular shape described in rodents, while the cSCN is located in the retrochiasmatic area. As expected, VIP-immunoreactive (ir) neurons were observed in the ventral part of mSCN. AVP-ir neurons were located in the rSCN and mSCN. Results also showed the presence of OT-ir and TH-ir neurons which seem to be a peculiarity of the camel SCN. OT-ir neurons were either scattered or gathered in one isolated cluster, while TH-ir neurons constituted two defined populations, dorsal parvicellular and ventral magnocellular neurons, respectively. TH colocalized with VIP in some rSCN neurons. Moreover, a high density of Met-Enk-ir, 5-HT-ir and NPY-ir fibers were observed within the SCN. Both the cytoarchitecture and the distribution of neuropeptides are unusual in the camel SCN as compared to other mammals. The presence of OT and TH in the camel SCN suggests their role in the modulation of circadian rhythms and the adaptation to photic and non-photic cues under desert conditions.

Daily regulation of body temperature rhythm in the camel (Camelus dromedarius) exposed to experimental desert conditions

In the present work, we have studied daily rhythmicity of body temperature (Tb) in Arabian camels challenged with daily heat, combined or not with dehydration. We confirm that Arabian camels use heterothermy to reduce heat gain coupled with evaporative heat loss during the day. Here, we also demonstrate that this mechanism is more complex than previously reported, because it is characterized by a daily alternation (probably of circadian origin) of two periods of poikilothermy and homeothermy. We also show that dehydration induced a decrease in food intake plays a role in this process. Together, these findings highlight that adaptive heterothermy in the Arabian camel varies across the diurnal light–dark cycle and is modulated by timing of daily heat and degrees of water restriction and associated reduction of food intake. The changed phase relationship between the light–dark cycle and the Tb rhythm observed during the dehydration process points to a possible mechanism of internal desynchronization during the process of adaptation to desert environment. During these experimental conditions mimicking the desert environment, it will be possible in the future to determine if induced high‐amplitude ambient temperature (Ta) rhythms are able to compete with the zeitgeber effect of the light–dark cycle.

e12151

In the Arabian camel, the “adaptative heterothermy” is characterized by a daily alteration (probably of circadian origin) of two periods. The findings highlight that adaptative heterothermy varies across the diurnal light–dark cycle and is modulated by timing of daily heat and degrees of water restriction and associated reduction of food intake.

Entrainment of the circadian clock by daily ambient temperature cycles in the camel (Camelus dromedarius)

In mammals the light-dark (LD) cycle is known to be the major cue to synchronize the circadian clock. In arid and desert areas, the camel ( Camelus dromedarius) is exposed to extreme environmental conditions. Since wide oscillations of ambient temperature (Ta) are a major factor in this environment, we wondered whether cyclic Ta fluctuations might contribute to synchronization of circadian rhythms. The rhythm of body temperature (Tb) was selected as output of the circadian clock. After having verified that Tb is synchronized by the LD and free runs in continuous darkness (DD), we submitted the animals to daily cycles of Ta in LL and in DD. In both cases, the Tb rhythm was entrained to the cycle of Ta. On a 12-h phase shift of the Ta cycle, the mean phase shift of the Tb cycle ranged from a few hours in LD (1 h by cosinor, 4 h from curve peaks) to 7–8 h in LL and 12 h in DD. These results may reflect either true synchronization of the central clock by Ta daily cycles or possibly a passive effect of Ta on Tb. To resolve the ambiguity, melatonin rhythmicity was used as another output of the clock. In DD melatonin rhythms were also entrained by the Ta cycle, proving that the daily Ta cycle is able to entrain the circadian clock of the camel similar to photoperiod. By contrast, in the presence of a LD cycle the rhythm of melatonin was modified by the Ta cycle in only 2 (or 3) of 7 camels: in these specific conditions a systematic effect of Ta on the clock could not be evidenced. In conclusion, depending on the experimental conditions (DD vs. LD), the daily Ta cycle can either act as a zeitgeber or not.

Estimation of the liveweight of working mules in Morocco from their body measurements

During March 2001, 117 working mules, randomly chosen from four markets in Morocco, were weighed and a series of body measurements recorded; their age and body condition score were also recorded. Linear regression techniques were used to derive a 'best fit' equation for predicting liveweight from the other variables. For the working mules weighing between 131 and 391 kg the best prediction equation using two variables was: liveweight (kg) = -33 + 2.8 x heart girth (cm)+1.36 x length (cm). Other prediction equations available for estimating the liveweight of equidae were tested on the data, but in all cases they significantly overestimated the weights of the Moroccan mules.

Regeneration of neurosecretory axons into various types of intrahypothalamic grafts is promoted by the absence of blood brain barrier: fine structural analysis

Isogenous grafts of neural lobe and optic nerve and autologous grafts of sciatic nerve were placed into contact with the intrahypothalamically transected hypothalamo-neurohypophysial tract, and their fine structural characteristics examined at various time periods thereafter. The vascular bed of neural lobe grafts is composed primarily of fenestrated capillaries, that are permeable to blood-borne HRP throughout the entire experimental period. The microvasculature of sciatic nerve grafts consists of continuous, as well as fenestrated capillaries, which are similarly permeable to HRP. Fenestrated capillaries and HRP leakage in optic nerve grafts are observed at 10 days, but only in grafts located ventrally in the hypothalamus at 30 days. Neurosecretory axon regeneration is seen only in grafts or adjacent hypothalamus where the blood-brain barrier is breached. Regenerating axons are closely associated with the specific glial cells of the respective graft. Based on these observations, we conclude that blood-borne factors are necessary to initiate and sustain regeneration of transected neurosecretory axons, and that such regeneration occurs only in the presence of glial cells.

Regeneration of neurosecretory axons into various types of intrahypothalamic graft is promoted by the absence of the blood-brain barrier: a neurophysin-immunohistochemical and horseradish peroxidase-histochemical study

In order to test the hypothesis that neurosecretory axon regeneration occurs only in the presence of specific vascular, perivascular, and glial microenvironments, isografts of neural lobe and optic nerve and autografts of sciatic nerve were transplanted into the hypothalamo-neurohypophysial tract at the lateral retrochiasmatic area of adult male rats. The integrity of the blood-brain barrier (BBB) to intravenously administered horseradish peroxidase (HRP), the regenerative process of neurosecretory axons, and functional recovery from lesion-induced diabetes insipidus were analyzed at 18 hr, 36 hr, 10 days, 30 days, and 80 days postsurgery. Neurophysin-positive axons invaded all grafts, as well as perivascular spaces of the adjacent hypothalamus. Wherever neurosecretory axon regeneration occurred, the BBB was breached. Reestablishment of the BBB was paralleled by a decrease in both density and staining intensity of regenerated neurophysin-positive axons. These observations illustrate that neurosecretory axon regeneration is tributary of the absence of BBB. It is speculated that blood-borne factors, provided when the BBB is breached, initiate and sustain neurosecretory axon regeneration. In addition, products of glial elements may enhance or complement the above stimulatory processes.

Estimation of the liveweight and body condition of working donkeys in Morocco

The age, sex, liveweight and body measurements (heart girth, umbilical girth, height, length from elbow to tuber ischii and circumference of the foreleg cannon bone) of 516 donkeys used to transport goods in Morocco were recorded. There were few donkeys over 12 years of age. For adult donkeys weighing from 74 to 252 kg, the best equation with only one variable for predicting liveweight was: liveweight (kg) = heart girth (cm)2.65/2188. The inclusion of two variables improved the prediction marginally, but the addition of further variables gave little further improvement. The best prediction equation for adult donkeys was: liveweight (kg) = (heart girth [cm]2.12 x length [cm]0.688)/380. For donkeys under three years of age, weighing from 52 to 128 kg, the best prediction equation was: liveweight (kg) = (umbilical girth [cm]1.41 x length [cm]1.09)/1000. Other liveweight prediction equations for donkeys and horses were tested on the data and tended to overestimate the weight of these working donkeys. A subjective method for assessing the body condition of the donkeys was developed, using a scale from 1 (emaciated) to 9 (obese).

An immunohistochemical and fine-structural analysis of peptidergic hypothalamic neurosecretory axon regeneration into the leptomeninges of the rat

Regeneration of severed hypothalamic peptidergic neurosecretory axons into the ventral pia-arachnoid was observed in rats at the light microscopic and fine-structural levels. A temporal increase occurred in the number of neurophysin-positive axons regenerating into the leptomeninges for distances up to 3.3 mm by 40 days post-lesioning. A consistent pattern of parallel, meshed and clustered axons, occurring either singly or in bundles, was present within the connective tissue, while plexus and bundles were observed in association with leptomeningeal blood vessels. Axons were characterized by preterminal and terminal dilatations. Neurosecretory granulated vesicles occurred throughout axons. The presence of microvesicles at contact points with basal lamina suggests the possibility of hormone release. Most axons were arranged as fascicles associated closely with basal lamina-bounded support cells whose thin lamellar processes wrapped single axons or fascicles of axons. We conclude, therefore, that cellular and intercellular leptomeningeal microenvironments support and sustain the growth and regeneration of transected neurosecretory axons.