Non-invasively assessing disturbance and stress in laboratory rats by scoring chromodacryorrhoea

In rats, like many rodents, Harderian glands next to the orbits secrete porphyrins, lipids and other compounds. High levels of secretion lead to chromodacryorrhoea (red or "bloody" tears), often taken as a sign of stress or disease. Here, we developed a scoring system for recording chromodacryorrhoea in a quantitative way, and investigated whether the low-level, transient Harderian secretions of normal, healthy rats correlate with low to moderate levels of stress or disturbance. Rather than exposing our subjects (24 Lister Hoodeds, housed in 11 single-sex cages) experimentally to stressors, we made opportunistic use of three likely sources of low-level stress within the unit: 1) building maintenance work, taking several hours and involving several potential stressors; 2) visits by unfamiliar humans, and the other mild sources of disturbance normal in an animal unit; and 3) social status within the cage. The mean daily chromodacryorrhoea score increased most with the severe disturbance of building maintenance work (F1,9 = 602.67, p < < 0.0001), and also increased--though to a lesser extent--with the mild disturbance of visitors and similar (F1,9 = 8.77, p = 0.008), while being the subordinate member of a cage-group had a smaller effect still (F1,6 = 7.86, p = 0.03). Individual rats scored consistently across treatment conditions, and there was also significant inter-observer reliability between independent scorers. We therefore suggest that scoring chromodacryorrhoea could be a simple, practical and non-invasive way of sensitively assessing the impact on rats of housing, husbandry, or procedures.

Alligator tears: a reevaluation of the lacrimal apparatus of the crocodilians

The Harderian gland is a poorly understood anterior ocular gland that occurs in most terrestrial vertebrates. Numerous extraorbital functions have been ascribed to the Harderian gland, principally based on its association with the nasolacrimal duct. Few studies have centered on archosaurs and the majority of those available focused solely on the Harderian gland of birds. Little is known about the lacrimal apparatus of the crocodilians. We examined the lacrimal apparatus of several specimens of Alligator mississippiensis anatomically, histologically, and histochemically and studied the embryogenesis of this system. The nasolacrimal duct possesses a distal secretory area, which is more convoluted than that of typical mammals or lepidosaurs. The alligator Harderian gland possesses a unique combination of characteristics found in lepidosaurs, birds, and mammals. Like that of both mammals and lepidosaurs, it is a large, tuboloacinar gland that appears to secrete both mucoprotein and lipids. However, the presence of blood vessels and immune cells is reminiscent of that of the avian Harderian gland. The immunogenesis of the alligator Harderian gland appears to be tied to the development of the vascular system. The presence of a distinct palpebral gland in the anterior aspect of the ventral eyelid is a feature unique to alligators. Based on position, this gland does not appear to be homologous to the anterior lacrimal gland of lepidosaurs. Lymphatic aggregations were also found in the palpebral gland. The presence of interstitial immune cells in the orbital glands of alligators suggests that the alligator lacrimal apparatus, like that of birds, may play a role in the head-associated lymphatic tissue system.

Septomaxilla of nonmammalian synapsids: soft-tissue correlates and a new functional interpretation. DELETE

The function of the septomaxilla of nonmammalian synapsids has long been problematic. Distinctive features of this bone, including a prominent intranarial process and a septomaxillary canal and foramen, are characteristic of pelycosaurs and nonmammalian therapsids, but are lost in their mammalian descendants. Numerous contradictory reconstructions have been proposed for the soft anatomy associated with the septomaxilla of nonmammalian synapsids. This review supports the following conclusions: 1) No particular correlation exists between the septomaxilla and the vomeronasal organ (VNO), and the most likely location for the VNO is on the dorsal surface of the palatal process of the vomer; 2) The most likely occupant of the septomaxillary canal is the nasolacrimal duct, which opened either anterior or medial to the intranarial process, near the opening of the VNO duct; and 3) The occupant of the septomaxillary foramen remains uncertain. These conclusions suggest that the functional significance of the septomaxilla in the nonmammalian synapsids is tied to that of the nasolacrimal duct. The association of this duct and the VNO in these animals resembles the condition in Recent amphibians and lepidosaurs, in which the nasolacrimal duct supplies orbital fluids to the VNO, apparently to enhance vomeronasal function. The peculiar shape of the synapsid septomaxilla may have served to collect vomeronasal odor molecules. The changes of the septomaxilla in early mammals, and its nearly complete loss in extant mammals, are probably correlated with a dissociation of the nasolacrimal duct and VNO, and functional changes in both structures.