Septal organ

A possible alternative is the microvillous part of the chemosensory epithelium in the Organ of Rodolfo-Masera (Septal Organ), which is VN-like (Taniguchi etal., 1993). This mixed receptor population requires much further study since it could prove to have intermediate odourant sensitivities (Giannetti et al., 1995). Its distribution and function(s) are still incompletely known however it is sufficiently widespread, from Opossums to Rodents, to warrant an intensive survey (Rodolfo-Masera, 1943 Kratzing, 1978 Giannetti et al., 1992 and 1995). 

The higher vertebrates retained the basic Nervus termitialis, a VN-associated chemoreceptive neurai network (Fig. 2.9) with some cognate functions (Chap. 5 and Murphy, 1998). In mammals, an apparently unique and enigmatic OR cell cluster with a separable MOB input occurs. This minor structure (Fig. 2.10), the Septal Organ (of Masera), is possibly adaptive, has no peripheral connection to the VNO, and its capacity for central modulation of MOS and or AOS input is unknown (Naguro, 1984 Marshall, 1986). 

Fig. 2.10 Nasal chemoreceptive systems (Rodent) — chemosensory and autonomic fibres Masera s organ (= Septal Organ) and NT, and vasomotor (NP and Ethmoidal) in adult hamster (from Meredith, 1983).

Giannetti N., Saucier D. and Astic L. (1992). Organization of the septal organ projection to the main olfactory bulb in adult and newborn rats. J Comp Neurol 323, 288-298. 

Giannetti N., Pellier V., Oestreicher A.B. and Astic L. (1995). Immunocytochemical study of the differentiation process of the Septal Organ of Masera in developing rats. Dev Brain Res 84, 287-293. 

Apart from taste, vertebrates have five different chemoreceptor systems for airborne chemosignals the main olfactory system, the vomeronasal organ (VNO), the trigeminal nerve, the septal organ of Masera, and the nervus termi-nalis. They each will be discussed in turn. All five are fully functional in most mammals (Fig. 5.1). 

The septal organ is a small patch of sensory epithelium on the wall of the septum, in the anterior part of the nasal cavity, and ventral to the olfactory epithelium. It is found primarily in rodents, has chemical receptors similar to olfactory receptors, and is sensitive to volatile odorants. It projects into the main olfactory bulb, but not into the accessory olfactoiy bulb (Pedersen and Benson, 1986). Because of its forward location, the septal organ may serve as an early-warning system that arouses resting or sleeping animals when volatiles are present (Wysocki, 1989). 

Pedersen, R. E. and Benson, T. E. (1986). Projection of septal organ receptor neurons to the main olfactoiy bulb in tats.JournalofComparativeNeurology 151,555-562. 

Septal organ function, like that of the terminal nerve, is obscure. The organ is apparently present in both mammals and birds. Little information is available on the biological importance of this system, although it may serve to trigger sniffing behavior in canines (D.A. Marshall, personal communication, 1985). 

Fig. 2.4 Displacement of the N-P duct caudally and intra-nasai transfer nasal aperture of the organ (VNd) on the rostral septum in (a) rodents, (b) lagomorphs, and (c) interconnection of VNd i— to N-Pd by sub-septal gutter in rat (from Wysocki and Meredith, 1991 Wohrmann-Repenning, 1981a and b).

The vasculature is established by the 18th day of gestation in rats, and comes from the arterial supply as the anterior cerebral vessel, eventually entering the basal lamina via septal tributaries of the olfactory artery (Szabo, 1988). Unlike the MOE, the organ s capillaries penetrate in loops into the neuroepithelium. Blood from the vomeronasal complex arrives for collection in the vomeronasal vein, as described earlier [Fig. 2.11(a)]. The establishment of the highly vascular columnar complexes seen in the ophidian organ has not been correlated with functional development (c.f. Wang and Halpem, 1980 Holtzman and Halpem, 1990). 

Taniguchi K., Arai T. and Ogawa K. (1993). Fine-structure of the septal olfactory Organ of Masera, and its associated gland in the Golden Hamster. J Vet Med Sci 5, 107-116. 

Infective endocarditis (IE) is a serious infection affecting the lining and valves of the heart. While this disease is mostly associated with infection of the heart valves, the septal defects may become involved as well. Infections also occur in patients with prosthetic or mechanical devices, such as mechanical heart valves or who are intravenous drug users (IVDUs). Bacteria is the primary cause of IE however, fungi and atypical organisms also can be responsible pathogens. 

Kratzing, J.E. 1978. The olfactory apparatus of the bandicoot fine structure and the presence of a septal olfactory organ. J. Anat., 125, 601—613. 

Absence of dense interstitial fibrosis Organizing pneumonia is not the prominent feature Diffuse, severe alveolar septal inflammation is absent Fibrosing pattern ... 

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