The rostral nasal anatomy of two elephant shrews.

The nasal anatomy of Elephantulus brachyrhynchus and E. myurus shows adaptations needed for a long, mobile snout with no special chemosensory features. Olfactory and vomeronasal neuroepithelia do not extend rostral to the nasal opening of the incisive ducts. Their fine structure presents no unusual features. Separate dorsal, lateral and ventral cartilages and fenestrations in the septal cartilage permit snout flexibility. Dorsal and ventral tubular glands extend the whole length of the snout under the dermis but only release their secretions at the tip, together with the products of the nasolacrimal and lateral nasal gland ducts. These secretions may protect the bare rostral epithelium from the chemical defences of termites and ants, which are major food items. A ventral groove in the snout communicates directly with the sulcus of the incisive papilla on the rostral palate. The oral openings of the incisive ducts also lie within the sulcus. Variability in the relation of the vomeronasal duct to the incisive duct and in the presence of taste buds on the incisive papilla in the two species of Elephantulus studied here limit their value as evidence of relationships between elephant shrews and other insectivores and prosimians.

Ascorbic acid in fetal rat brain.

Ascorbic acid in fetal rat brain increases from 374 mg/g on the 15th day of gestation to 710 mg/g by the 20th day and remains at that level until birth. There is an 18% drop from this plateau after birth.

The structure and distribution of nasal glands in four marsupial species.

The structure and distribution of nasal glands in four marsupial species were studied by light and electron microscopy. The species studied were the honey possum (Tarsipes rostratus), the bandicoot (Isoodon macrourus), the koala (Phascolarctos cinereus) and the agile wallaby (Macropus agilis). Glands were grouped and described according to their location. Those of general distribution (goblet cells and olfactory glands) were similar in structures and distribution in all specimens. Glands of the lateral nasal wall include the lateral nasal, maxillary sinus and turbinate glands. The lateral nasal and maxillary sinus glands were absent in the adult koala but occupied large areas in the other species. Turbinate glands were best developed rostrally and ventrally in the nasal cavity. On the nasal septum, Tarsipes and Isoodon had well developed glands associated with vascular 'swell bodies'. These were poorly developed to Macropus though septal glands were abundant. 'Swell bodies' were absent in Phascolarctos and glands were sparse. Tubular vomeronasal glands were present in all species and most extensive in Tarsipes. In Isoodon, there was a posterior ventral septal gland associated with the septal olfactory organ. The fine structural features of secretory cells and ducts are described and their potential role discussed in terms of chemoreception and temperature and humidity control.

The anatomy and histology of the nasal cavity of the koala (Phascolarctos cinereus).

The anatomy of the nose of the koala was studied from fixed 0.5 cm thick sections of a whole head. Right and left nasal cavities are separated by a slender septum which does not exhibit 'swell bodies'. Dorsal and ventral conchae are simple curved plates without elaborate scrolls; the ventral concha is recurved to form a bulla. The nasal cavity communicates with confluent rostral maxillary and frontal air sinuses. A ventrocaudal maxillary sinus opens from the ventral meatus close to the choanae. There is a frontal sinus dorsocaudal to the ethmoid region which does not communicate with the nasal cavity. Nasal and oral cavities communicate via incisive ducts, opening just rostral to the vomeronasal ducts. The vomeronasal organ extends from the level of the fourth incisor to the first cheek tooth. The histology of the nasal area was examined by light and electron microscopy. Stratified squamous epithelium extends from the external nares to the incisive duct; nerve endings are frequent in association with its basal cells. Respiratory epithelium lines the nasal cavity proper, olfactory epithelium covers the ethmoturbinate bones, caudal dorsa concha and caudal septum, and sensory epithelium lines the medial aspect of the vomeronasal organ. Nasal secretions are provided by goblet cells and conchal and septal glands in respiratory areas, and by Bowman's and vomeronasal glands in the sensory areas. There are no lateral nasal glands, maxillary sinus glands or swell body glands.

Regional variation in respiratory epithelium of the nasal cavity of the bandicoot (Isoodon macrourus).

The non-olfactory ciliated epithelium of the nasal cavity was investigated in the bandicoot (Isoodon macrourus), a small ground-dwelling marsupial. Two distinct epithelial types were identified and designated conchal and septal. Conchal epithelium is non-secretory. It covers most of the naso- and maxilloturbinates, the lateral nasal wall, and part of the maxillary sinus. Septal epithelium contains mucus-secreting goblet cells. Rostrally, it covers the nasal septum and mid-ventral floor of the nasal cavity. Further caudally it lies on the ventral part of the septum and ventrally facing parts of naso- and ethmoturbinates. It corresponds closely to most published descriptions of respiratory epithelium. Ciliated and basal cells are common to both types. Conchal epithelium has a nonciliated domed cell with a rounded surface projecting into the ciliary border. This epithelium has a rich innervation and axon terminals are frequent almost to the cell surface. Septal epithelium contains goblet cells whose appearance varies according to secretory activity, and two rarer cells of unknown function, brush and pale cells, which are also seen in the olfactory epithelium of the bandicoot.

The olfactory apparatus of the bandicoot (Isoodon macrourus): fine structure and presence of a septal olfactory organ.

The structure and extent of olfactory epithelium in the bandicoot (Isoodon macrourus) were examined by light and electron microscopy. Sensory epithelium covers most of the dorsal conchae, though non-sensory epithelium lines ventrally facing scrolls. The middle conchae are partly covered by olfactory epithelium, the proportion of olfactory to ciliated respiratory epithelium increasing caudally. Ventral conchae are lined by non-sensory ciliated epithelium. The nasal septum ends short of the floor of the nasal cavity in its caudal two thirds. It is covered dorsally by olfactory epithelium. The ventral margin has rounded lateral extensions which carry the isolated strips of olfactory epithelium which form the septal olfactory organ. The fine structure of the olfactory epithelium is the same in all areas. Cell types include olfactory receptors, supporting cells, two types of basal cell and rarer pale and brush cells. There is considerable morphological variation in olfactory cells, and evidence suggestive of continuing turnover in the receptor cell population.

Organization of desmosomes in Bowman's gland duct cells in a marsupial.

Non-secretory cells lining the ducts of Bowman's gland in the olfactory epithelium of the bandicoot (Isoodon macrourus) are united below the duct lumen by an unusually well-organized series of desmosomes linked by conspicuous fibrillar bundles with long mitochondria aligned close to the bundles. It is suggested that these junctional specializations may help to maintain an intact duct lumen in a part of the epithelium with considerable intercellular space.

The fine structure of the olfactory and vomeronasal organs of a lizard (Tiliqua scincoides scincoides).

Olfactory epithelium in Tiliqua scinoides is of a loosely packed pseudostratified type. It receives secretion from the supporting cells and the underlying glands of Bowman. Its surface bears microvilli and cilia from sensory cells and microvilli from supporting cells. The vomeronasal epithelium is also pseudostratified but higher and more closely packed. Its surface carries microville from sensory and supporting cells but lacks cilia. Vascular connective tissue penetrates it almost to the epithelial surface but is always outlined by basal cell processes and a basal lamina. There are no secretory cells in or under the sensory epithelium but some cells in the epithelium of the mushroom body contain secretion granules. Sensory cells of both epithelia are bipolar neurons. The perikarya of the vomeronasal cells are more neuronal in character. Axonic processes are similar in both, dendrites are distinctive. Olfactory dendrites end in rounded rods bearing microvilli and cilia of an unusual type. Microville with filamentous cores occur on vomeronasal dendrites. There are no cilia, but 2-6 centrioles appear below the cell surface. Basal cells are structurally similar in both epithelia, but axonic processes of olfactory cells are surrounded by supporting cell processes, while vomeronasal axonic processes are surrounded by basal cells before they leave the epithelium. The presence of cilia and microville on the surface of the sensory cells is discussed in relation to the physical conditions surrounding them.