Daily Aa-nat gene expression in the camel (Camelus dromedarius) pineal gland

Dromedary camel: A model of heat resistant livestock animal

Camels are highly adapted to harsh environments. The dromedary camel is adapted to a wide range of arid and semi-arid conditions. The aim of the present paper is to review some of the key adaptation characteristics of the dromedary and how they affect reproductive patterns. Special attention is given to the reproductive seasonality and interaction between lactation and reproduction. Adaptive mechanisms are described including some of the recent molecular aspects with respect to heat shock protein expression in camels.

Effect of short artificial lighting and low temperature in housing rooms during non-rutting season on reproductive parameters of male dromedary camels

Ten dromedary mature males were used to study the effects of short artificial lighting and low temperature on the reproductive behavior, testicular size, semen quality and hormone during the non-rutting season and subsequent rutting season. Bulls were allocated into two groups: the first group were subjected to natural daylight and temperature and used as a control. The second group was housed individually in light and temperature controlled rooms in which artificial light (300 lux) was used for 10 h/d, and the temperature was 25.28 ± 0.21 °C. The trial was initiated in mid-June and continued for 10 weeks in the non-rutting season. The reproductive parameters of all animals in the control and room groups were evaluated once every two weeks. The reproductive parameters of all animals in the control and room groups were re-evaluated during the rutting season of the same year. A significant (P < 0.05) increase in the morphometry of the testes, scrotum, libido, and reaction time score, as well as serum melatonin and testosterone levels, was observed in the treatment non-rutting season (TNRS) group compared to in the control non-rutting season (CNRS) group. The testicular volume, reaction time score, serum melatonin, and testosterone were significantly (P < 0.05) higher in the treatment rutting season (TRS) group than in the control non-rutting season (CRS) group. Improvement in the semen parameters were observed in the TNRS and TRS groups compared to in the CRS group. In conclusion, these results demonstrate that short artificial lighting and low temperature can induce rutting out of season and improve the reproductive parameters of dromedary males during the subsequent rutting season.

Shortened daily photoperiod during the non-breeding season can improve the reproductive performance of camel bulls (Camelus dromedarius)

The effects of a shortened photoperiod on the reproductive performance and hormones of mature dromedary camel bulls (Camelus dromedarius) were evaluated. A group of 6 bulls were blindfolded to induce a daily photoperiod that was ∼2.55 h shorter than the natural day length (10.83L:13.17D), whereas 6 others served as the control group. The trial started in June and continued for 10 weeks during the non-breeding season. The reproductive performance of all animals was evaluated weekly during this time and also during the breeding season, starting in December and continuing for 10 weeks. Camel bulls in the treatment group showed a significant (p < 0.05) increase in testicular volume, scrotal circumference, sexual desire, reaction time, and mating ability scores, and serum melatonin and testosterone concentrations, relative to the control group, during the non-breeding season. In addition, sexual desire and reaction time and mating ability scores were significantly (p < 0.05) higher in the treatment group than in the control during the breeding season. There was no significant difference between the treatment groups in both seasons and the control group in the breeding season regarding semen volume, sperm cell concentration, total motility, progressive motility, plasma membrane integrity, and viability. Shortening the daily photoperiod by blindfolding can improve the reproductive performance of dromedary camel bulls during the non-breeding season and the following breeding season. This simple, inexpensive, and easily applicable method can enable breeders to collect semen of acceptable quality during the non-breeding season.

Effects of melatonin implants on the reproductive performance and endocrine function of camel (Camelus dromedarius) bulls during the non-breeding and subsequent breeding seasons

This study aimed to evaluate the effects of melatonin implants on the reproductive performances and hormone levels of dromedary (Camelus dromedarius) bulls during the non-breeding and subsequent breeding seasons. Fourteen mature dromedary bulls were divided into a control group (n = 7) and a group that was implanted with melatonin (n = 7) twice, at the beginning of the study and 35 days later. The trial started on the 17th June and continued for 10 weeks during the non-breeding season. Reproductive performances of animals in the control and melatonin groups were evaluated weekly during the non-breeding season [control non-breeding (CNB) and melatonin non-breeding (MNB) groups, respectively] and evaluated again during the subsequent breeding season [control breeding (CB) and melatonin breeding (MB) groups, respectively], which started on the 6th December and continued for 10 weeks. MNB bulls had greater (P ≤ 0.05) scrotum circumference and testicular volume, sexual desire, reaction time and mating ability scores, and serum melatonin and testosterone concentration values (24.91 ± 0.26 cm, 271.00 ± 7.81 cm³, 2.31 ± 0.13, 2.03 ± 0.22, 2.26 ± 0.09, 23.90 ± 0.05 pg/mL and 2764.51 ± 137.02 pg/mL, respectively) than the CNB group (23.63 ± 0.05 cm, 199.21 ± 3.27 cm³, 1.00 ± 0.00, 0.00 ± 0.00, 1.00 ± 0.00, 9.46 ± 0.08 pg/mL and 1872.41 ± 264.89 pg/mL, respectively). The scrotum and testes, reaction time score, proportion of bulls refusing to mount, and serum melatonin values were significantly higher in MB than CB bulls (P ≤ 0.05). Progressive motility (PM), average pathway velocity, straight-line velocity, curvilinear velocity (VCL), linearity, straightness (STR), wobble, beat cross frequency (BCF), livability, and DNA integrity were significantly higher in MB than CB bulls (P ≤ 0.05). PM, VCL, STR, amplitude of lateral head displacement, BCF, and livability were significantly higher in MNB than CB bulls (P ≤ 0.05). In conclusion, melatonin implants improved the reproductive performance of bulls during the non-breeding and subsequent breeding seasons.

Effect of Melatonin Implants during the Non-Breeding Season on the Onset of Ovarian Activity and the Plasma Prolactin in Dromedary Camel

To examine a possible control of reproductive seasonality by melatonin, continual-release subcutaneous melatonin implants were inserted 4.5 months before the natural breeding season (October-April) into female camels (Melatonin-treated group). The animals were exposed to an artificial long photoperiod (16L:8D) for 41 days prior to implant placement to facilitate receptivity to the short-day signal that is expected with melatonin implants. The treated and control groups (untreated females) were maintained separately under outdoor natural conditions. Ovarian follicular development was monitored in both groups by transrectal ultrasonography and by plasma estradiol-17β concentrations performed weekly for 8 weeks and then for 14 weeks following implant insertion. Plasma prolactin concentrations were determined at 45 and 15 days before and 0, 14, 28, 56, and 98 days after implant insertion. Plasma melatonin concentration was determined to validate response to the artificial long photoperiod and to verify the pattern of release from the implants. Results showed that the artificial long photoperiod induced a melatonin secretion peak of significantly (P < 0.05) shorter duration (about 2.5 h). Melatonin release from the implants resulted in higher circulating plasma melatonin levels during daytime and nighttime which persisted for more than 12 weeks following implants insertion. Treatment with melatonin implants advanced the onset of follicular growth activity by 3.5 months compared to untreated animals. Plasma estradiol-17β increased gradually from the second week after the beginning of treatment to reach significantly (P < 0.01) higher concentrations (39.2 ± 6.2 to 46.4 ± 4.5 pg/ml) between the third and the fifth week post insertion of melatonin implants. Treatment with melatonin implants also induced a moderate, but significant (P < 0.05) suppressive effect on plasma prolactin concentration on the 28th day. These results demonstrate that photoperiod appears to be involved in dromedary reproductive seasonality. Melatonin implants may be a useful tool to manipulate seasonality and to improve reproductive performance in this species. Administration of subcutaneous melatonin implants during the transition period to the breeding season following an artificial signal of long photoperiod have the potential to advance the breeding season in camels by about 2.5 months.

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.

Melatonin signaling in T cells: Functions and applications

Melatonin affects a variety of physiological processes including circadian rhythms, cellular redox status, and immune function. Importantly, melatonin significantly influences T-cell-mediated immune responses, which are crucial to protect mammals against cancers and infections, but are associated with pathogenesis of many autoimmune diseases. This review focuses on our current understanding of the significance of melatonin in T-cell biology and the beneficial effects of melatonin in T-cell response-based diseases. In addition to expressing both membrane and nuclear receptors for melatonin, T cells have the four enzymes required for the synthesis of melatonin and produce high levels of melatonin. Meanwhile, melatonin is highly effective in modulating T-cell activation and differentiation, especially for Th17 and Treg cells, and also memory T cells. Mechanistically, the influence of melatonin in T-cell biology is associated with membrane and nuclear receptors as well as receptor-independent pathways, for example, via calcineurin. Several cell signaling pathways, including ERK1/2-C/EBPα, are involved in the regulatory roles of melatonin in T-cell biology. Through modulation in T-cell responses, melatonin exerts beneficial effects in various inflammatory diseases, such as type 1 diabetes, systemic lupus erythematosus, and multiple sclerosis. These findings highlight the importance of melatonin signaling in T-cell fate determination, and T cell-based immune pathologies.

Phytomelatonin: assisting plants to survive and thrive

This review summarizes the advances that have been made in terms of the identified functions of melatonin in plants. Melatonin is an endogenously-produced molecule in all plant species that have been investigated. Its concentration in plant organs varies in different tissues, e.g., roots versus leaves, and with their developmental stage. As in animals, the pathway of melatonin synthesis in plants utilizes tryptophan as an essential precursor molecule. Melatonin synthesis is inducible in plants when they are exposed to abiotic stresses (extremes of temperature, toxins, increased soil salinity, drought, etc.) as well as to biotic stresses (fungal infection). Melatonin aids plants in terms of root growth, leaf morphology, chlorophyll preservation and fruit development. There is also evidence that exogenously-applied melatonin improves seed germination, plant growth and crop yield and its application to plant products post-harvest shows that melatonin advances fruit ripening and may improve food quality. Since melatonin was only discovered in plants two decades ago, there is still a great deal to learn about the functional significance of melatonin in plants. It is the hope of the authors that the current review will serve as a stimulus for scientists to join the endeavor of clarifying the function of this phylogenetically-ancient molecule in plants and particularly in reference to the mechanisms by which melatonin mediates its multiple actions.

Sonographic monitoring of early follicle growth induced by melatonin implants in camels and the subsequent fertility

The present study examined the effect of melatonin implants on follicle growth in dromedary camels two months ahead of their natural breeding season (December to March). Female camels (n = 6) were treated with melatonin implants at the dose rate of 1 implant per 28 kg body weight sc. Control camels (n = 6) were administered an SC placebo implant of 8 ml vitamin A. Ovarian ultrasonography was performed at weekly interval upto 7 weeks. Camels were mated with virile stud when a follicle (≥10 mm) was visible on either of the ovaries. Blood was collected on day 7, 9, 15, 20, 25 and 30 for assay of plasma progesterone and sonography performed at the same time. Small follicles (2-3 mm) appeared around the periphery of ovaries in 83.3% of camels by day 7 and in 100% camels by day 14. By the end of 7th week an ovulatory size follicle (≥1.0 cm) could be observed in 83.3% of treated camels, and these camels were mated with virile studs. In control group, small follicles appeared at the periphery of ovaries only in 66.6% camels but did not progress in growth except in one camel (16.6%) however, ovulating size (≥10 mm) follicle was not observed in any camel by the end of 7th week. All treated camels ovulated and one treated camel became pregnant while early embryonic death occurred in one camel. Non-pregnant camels of both groups were mated during the breeding season. All camels of treatment group and 33.33% camels of control group became pregnant by the end of breeding season (April 2010). It was concluded that melatonin implants can augment the follicle growth in lactating camels ahead of the breeding season and pregnancy can occur on mating. Fertility of treated camels during the breeding season is improved.

Differential resetting process of circadian gene expression in rat pineal glands after the reversal of the light/dark cycle via a 24 h light or dark period transition

Although studies involving the circadian response to time-zone transitions indicate that the circadian clock usually takes much longer to phase advance than delay, the discrepancy between the circadian resetting induced by photoperiod alteration via a dark or light period transition has yet to be investigated. In mammals, the pineal gland is an important component in the photoneuroendocrine axis, regulating biological rhythms. However, few studies have systematically examined the resetting process of pineal clock-gene expression to date. We investigated the resetting processes of four clock genes (Bmal1, Cry1, Per1, Dec1) and AANAT in the rat pineal gland after the light-dark (LD) reversal via a 24 h light or dark period transition. The resynchronization of the SCN-driven gene AANAT was nearly complete in three days in both situations, displaying similar resetting rates and processes after the differential LD reversals. The resetting processes of the clock genes were characterized by gene-specific, phase-shift modes and differential phase-shift rates between the two different LD reversal modes. The resetting processes of these clock genes were noticeably lengthened after the LD reversal via the light period transition in comparison to via the dark period transition. In addition, among the four examined clock genes, Per1 adjusted most rapidly after the differential LD reversals, while the rhythmic Cry1 expression adjusted most slowly.