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.

Main anatomical and histological features of the tonsils in the camel (Camelus dromedarius).

The tonsils, located around the pharyngeal cavity, constitute the first defence barrier against intruding microorganisms and antigens. The present work aimed to study the anatomical and histological aspects of camel tonsils in order to elucidate their role. The study was carried out on 12 camel heads fixed by infusion with 10 % neutral buffered formalin. A careful dissection of the oral cavity, the soft palate and the pharynx was conducted to explore the morphological aspect of different tonsils. Sagittal sections of some camel heads were also performed to explore their internal conformation, whereas the histological study was carried out on five specimens. All the six types of tonsils exist in the camel. Compared to other domestic species, they are well developed and all visible particularly the palatine one. The lingual, palatine, velar and paraepiglottic tonsils are arranged into closely assembled lymphoid follicles and show multitude crypt opennings into the oropharyngeal tube. The crypts epithelium is infiltrated with lymphoid cells allowing close contact with antigens. While the nasopharynx tonsils (pharyngeal and tubal) include loosely connected follicles which extend into the overlaying epithelium. The relatively great development and particular arrangement of the tonsils in the camel as well as the abundance of cryptic formations in all these tonsils constitute another aspect of adaptation and resistance of this species to its environment.

Seasonal variations in the nycthemeral rhythm of plasma melatonin in the camel (Camelus dromedarius).

Seasonal changes in the pattern of plasma melatonin were investigated in two groups of camels (Camelus dromedarius): 11 adult and six young camels. Animals were subjected to the outdoor conditions of a desert environment. Blood samples were taken at regular intervals of about 3 hr (added to particular samples at 1 hr before then 30 min and 1 hr after sunset, and 1 hr before and 1 hr after sunrise) for 24 hr at both solstices and equinoxes of the year. The plasma melatonin levels steeply increased soon after sunset and remained elevated throughout all the night. Then, melatonin concentrations progressively declined shortly before sunrise and returned to daytime basal levels 1 hr later. There was no seasonal variation in the amplitude or in the offset of the melatonin peak or in the daytime basal levels. The onset of the nocturnal peak was delayed by 2 hr in June at the summer solstice (P < 0.05), which can be related to the changes in night length between the two solstices. A significant effect of age was observed in all seasons. Melatonin levels were higher in the young camel group (fall equinox: P < 0.001; spring equinox: P < 0.01; winter solstice: P < 0.01; summer solstice: P < 0.05). The pattern of melatonin secretion in the camel showed a significant seasonal variation parallel to the photoperiodic changes of the year. The observed decline of melatonin levels during an extra-light pulse in the middle of the night indicates the light control of melatonin synthesis. It is not yet known if, in this low latitude desert region, the seasonal breeding period of the camel is cued by the photoperiod. The data obtained, however, clearly demonstrate that the camel has the capacity to follow and to integrate photoperiodic changes through melatonin changes.

Changes in neuronal metabolism in hypothalamic periventricular regions following acute alteration of cerebrospinal fluid composition in conscious rats.

Quantitative 2-deoxyglucose (2-DG) autoradiography was employed to determine the effect of elevating cerebrospinal fluid osmolality on neuronal metabolism of hypothalamic periventricular regions in conscious rats. Injection of hypertonic mannitol solution into the dorsal third ventricle had no significant effect on local cerebral glucose utilization, whereas administration into the ventral third ventricle resulted in a significant elevation in 2-DG uptake in only the posterior pituitary, median preoptic nucleus (MnPo), median eminence and suprachiasmatic nucleus. These results indicate the contribution of a synaptic connection in the MnPo in the activation of the osmoreceptor complex.