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.

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 (T_a) are a major factor in this environment, we wondered whether cyclic T_a fluctuations might contribute to synchronization of circadian rhythms. The rhythm of body temperature (T_b) was selected as output of the circadian clock. After having verified that T_b is synchronized by the LD and free runs in continuous darkness (DD), we submitted the animals to daily cycles of T_a in LL and in DD. In both cases, the T_b rhythm was entrained to the cycle of T_a. On a 12-h phase shift of the T_a cycle, the mean phase shift of the T_b 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 T_a daily cycles or possibly a passive effect of T_a on T_b. To resolve the ambiguity, melatonin rhythmicity was used as another output of the clock. In DD melatonin rhythms were also entrained by the T_a cycle, proving that the daily T_a 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 T_a cycle in only 2 (or 3) of 7 camels: in these specific conditions a systematic effect of T_a on the clock could not be evidenced. In conclusion, depending on the experimental conditions (DD vs. LD), the daily T_a cycle can either act as a zeitgeber or not.

Female mammals are classified into spontaneous and induced ovulators based on the mechanism eliciting ovulation. Ovulation in spontaneous species (e.g., human, sheep, cattle, horse, pigs, and most rodents) occurs at regular intervals and depends upon the circulating estradiol. However, in induced ovulators (e.g., rabbits, ferrets, cats, and camelids) ovulation is associated with coitus. In the later, various factors have been proposed to trigger ovulation, including auditory, visual, olfactory and mechanic stimuli. However, other studies have identified a biochemical component in the semen of induced ovulators responsible for the induction of ovulation and named accordingly ovulation inducing factor. In camelids, intramuscular or intrauterine administration of seminal plasma was shown to induce the preovulatory LH surge followed by ovulation and subsequent formation of corpus luteum. Recently, this ovulation inducing factor has been identified from seminal plasma as a neurotrophin, the nerve growth factor ß (ß-NGF). ß-NGF is well known as promoting neuron survival and growth, but in this case, it appears to induce ovulation through an endocrine mode of action. Indeed, ß-NGF may be absorbed through the endometrium to be conveyed, via the blood stream, to the central structures regulating the LH preovulatory surge. In this review we provide a summary of the most relevant results obtained in the field and we propose a working hypothesis for the central action of ß-NGF based on our recent demonstration of the presence of neurons expressing kisspeptin, a potent stimulator of GnRH/LH, in the camel hypothalamus.

Improvement of oat lines via introgression is an important process for food biochemical functionality. This work aims to evaluate the protective effect of phenolic compounds from hybrid Oat line (F11-5) and its parent (Amlal) on hyperglycemia-induced oxidative stress and to establish the possible mechanisms of antidiabetic activity by digestive enzyme inhibition. Eight phenolic acids were quantified in our samples including ferulic, p-hydroxybenzoic, caffeic, salicylic, syringic, sinapic, p-coumaric and chlorogenic acids. The Oat extract (2000 mg/kg) ameliorated the glucose tolerance, decreased Fasting Blood Glucose (FBG) and oxidative stress markers, including Superoxide dismutase (SOD), Catalase (CAT), Glutathione peroxidase (GPx), Glutathione (GSH) and Malondialdehyde (MDA) in rat liver and kidney. Furthermore, Metformin and Oat intake prevented anxiety, hypercholesterolemia and atherosclerosis in diabetic rats. In vivo anti-hyperglycemic effect of Oat extracts has been confirmed by their inhibitory activities on α-amylase (723.91 μg/mL and 1027.14 μg/mL) and α-glucosidase (1548.12 μg/mL & 1803.52 μg/mL) enzymes by mean of a mixed inhibition.