Choosing sheep (Ovis aries) as animal model for temporomandibular joint research: Morphological, histological and biomechanical characterization of the joint disc.

Preclinical trials are essential to the development of scientific technologies. Remarkable molecular and cellular research has been done using small animal models. However, significant differences exist regarding the articular behavior between these models and humans. Thus, large animal models may be more appropriate to perform trials involving the temporomandibular joint (TMJ). The aim of this work was to make a morphological (anatomic dissection and white light 3D scanning system), histological (TMJ in bloc was removed for histologic analysis) and biomechanical characterization (tension and compression tests) of sheep TMJ comparing the obtained results with human data. Results showed that sheep processus condylaris and fossa mandibularis are anatomically similar to the same human structures. TMJ disc has an elliptical perimeter, thinner in the center than in periphery. Peripheral area acts as a ring structure supporting the central zone. The disc cells display both fibroblast and chondrocyte-like morphology. Marginal area is formed by loose connective tissue, with some chondrocyte-like cells and collagen fibers in diverse orientations. Discs obtained a tensile modulus of 3.97±0.73MPa and 9.39±1.67MPa, for anteroposterior and mediolateral assessment. The TMJ discs presented a compressive modulus (E) of 446.41±5.16MPa and their maximum stress value (σmax) was 18.87±1.33MPa. Obtained results suggest that these animals should be considered as a prime model for TMJ research and procedural training. Further investigations in the field of oromaxillofacial surgery involving TMJ should consider sheep as a good animal model due to its resemblance of the same joint in humans.

Improvement of fertility in artificially inseminated ewes following vaginal treatment with misoprostol plus terbutaline sulphate.

The effect of vaginal administration of misoprostol plus terbutaline sulphate 6 h prior to artificial insemination (AI) upon the site of AI (vaginal or cervical) and fertility was studied using a total of 87 estrous synchronized Serra da Estrela ewes (control n = 42 and treated n = 45). Artificial insemination was performed using refrigerated semen at 54-55 h after sponge removal. Lambing rate (fertility) and prolificacy were compared between control and treated ewes. The effect of the site of semen deposition on fertility was also evaluated. Prolificacy rate was not different between control (1.5) and treated (1.59) ewes. The proportion of cervical AI achieved in control (45.2%) and treated (37.8%) ewes was not significantly different. Overall, fertility was significantly lower in control than in treated ewes (42.9% vs 64.4%; p < 0.04). Fertility following vaginal AI was significantly lower for control for than treated ewes (30.4% vs 60.7%; p < 0.03) but the difference was smaller and not significant for cervical AI (control 57.9% vs 70.6%). It was concluded that vaginal administration of misoprostol plus terbutaline sulphate 6 h prior to artificial insemination did not affect the proportion of cervical inseminations but significantly improved the fertility of treated ewes. Although needing confirmation, it was hypothesized that drugs might have induced local secretory modifications leading to an increase of cervical ability to retain more viable spermatozoa for fertilization.

Increased cervical electrical activity during oestrus in progestagen treated ewes: Possible role in sperm transport.

The aim of this investigation was to characterize the pattern of cervical myoelectrical activity (EMG) in the sheep, during the periovulatory period, after synchronization of oestrus with progestagen and eCG. EMG was measured with a computerised modular system in five ewes previously fitted with a pair of monopolar Teflon needle electrodes in the muscle layers of the cervix. Each ewe was submitted to oestrus synchronization treatment with intravaginal progestagen sponge during 12 days, and the administration of 500 IU of eCG at the withdrawal of sponge. EMG was recorded in each animal during 19 h, starting 44 h after withdrawal of sponge. The number and duration of events were determined every hour during the experiment. Two distinct event durations were identified: one lasting less than 200 s and another lasting between 300 and 500 s. The two types of events analysed (less than 200 s and lasting between 300 and 500 s) had a similar pattern during the period of observation although they were not in synchrony. For events lasting less than 200 s, activity increased between 48 and 50 h after sponge withdrawal, with the peak of activity being observed between 51 and 53 h. For events of 300-500 s duration, the peak of activity was observed between 48 and 50h after sponge withdrawal and activity was maintained until 51-53 h. The increase in cervical motility observed in progestagen-eCG treated ewes is in keeping with the increase in cervical activity observed by others in natural cycling animals, and suggests that exogenous hormones used in synchronization protocols had no deleterious action on cervical motility during periovulatory period. The enhanced activity of cervical muscle layer found around the time of mating and/or AI suggests it may play an important role as a regulatory mechanism of sperm transport. Taking advantage of the cervical responsiveness to various drugs, experimental modulation of cervical activity could be used to facilitate cervical sperm transport and consequent improve of fertility after cervical AI.