Immunoreactivity to insulin (Ins), somatostatin (Som), glucagon (Glu) and pancreatic polypeptide (PP) was found in 70%, 22%, 15% and 11% respectively of Houbara pancreatic endocrine islet cells. Whilst Ins occurred centrally and SOM was observed both in peripherally and centrally located islets, the other hormones were localised in peripheral islet cells; Som was also observed in neuronal cell bodies and nerve fibres. In addition, the islet cells contained substance P (SP) (65%) in the centre and vasoactive intestinal polypeptide (VIP) (2%) at the periphery. Immunoreactivity to choline acetyltransferase (ChAT), VIP and galanin (Gal) occurred in the walls of blood vessels located mainly at the periphery of islets. Occasionally, VIP and Gal immunoreactive varicose nerve terminals and ChAT immunoreactive cell bodies were also observed in the centre of islets. SP neuronal cell bodies were not observed but prominent SP immunoreactive varicose terminals were discernible in capillary walls within the islets. Neuropeptide Y (NPY) immunoreactive neurons were detected in neuronal cell bodies located mainly peripherally. Neuronal nitric oxide synthase (nNOS) immunoreactivity occurred in neuronal cell bodies and nerve fibres mainly at the periphery and also in centrally located islet endocrine cells. Immunoreactivity to tyrosine hydroxylase (TH) was similar in distribution to that of ChAT. In comparison with other avian species, the islets of the dorsal pancreatic lobe of the bustard contain all the peptidergic hormones normally present in the islets of other avian species, but are not segregated into dark A and light B cells. Many of the insulin containing cells also contained SP. The islets also contained several neuropeptides which are probably involved in their regulation.

Distribution of neuronal nitric oxide synthase (nNOS) has been studied in the enteric nervous system of the camel jejunum by immunohistochemistry. Immunoreactivity to nNOS was discernible in selective groups of neurons and nerve terminals in the myenteric and submucosal plexuses. 20 % of neurons within the myenteric and 8 % within the submucosal plexuses stained positive for nNOS. The immunoreactive neurons occurred both in groups and as solitary neurons in both the myenteric and submucosal plexuses. Whilst most of the neurons possessed tapering ends which appeared to point towards the circular muscle layer, a few seemed to point towards the longitudinal layer of the muscularis externa. Nerve fibres immunoreactive to nNOS, some of which possessed varicosities, were detected in the myenteric plexus and within the circular and longitudinal layers. The submucosal immunoreactive neurons and nerve fibres were observed mainly in the inner plexus of Meissner. Immunoreactivity to nNOS was not observed either in the mucosa of the gut or around blood vessels. It is concluded that nitric oxide synthase, which catalyzes the synthesis of nitric oxide, is present in the enteric nervous system of the camel jejunum where nitric oxide probably functions as an inhibitory neurotransmitter.

This study investigates the differences in the outward appearance and morphology of lacrimal glands, the morphology within the lacrimal acinar cells and the secretion of protein from acinar cells of young (3–5 months) and aged (20 and 24 months) male rats. The appearance of the glands, as seen by the naked eye, differed between the three age-groups. The lacrimal gland of young animals was a smooth pink tissue, while the tissue from aged animals appeared lobular and white in colour, thought to result from infiltration of fatty/connective tissue. Glands from 24 month old animals had a more pronounced lobular appearance than the glands from 20 month old animals. Light microscopy studies revealed that as the animals aged there was evidence of progressive morphological changes. These changes included thickening of the connective tissue sheath, chronic inflammation with increased infiltration by mast cells, patchy destruction of ductal and vascular tissues, enlargement of lacrimal ducts, luminal swelling of the acini, and changes in acinar type. Electron microscopy (EM) studies revealed the presence of 3 types of acini in the rat lacrimal gland: acini which contained only protein secretory granules (serous acini), acini which contained protein and mucous secretory granules (seromucous acini), and acini which contained only mucous secretory granules (mucous acini). In young glands the majority of acini were serous with a few seromucous acini and even fewer mucous acini. In aged glands there were significant reductions in serous acini (ANOVA; P<0.01) when compared to the young glands. In 20-month-old glands, there were marked increases in the percentage occurrence of seromucous acini, while in 24 month old glands, there were large increases in the relative number of mucous acini. Qualitative EM studies demonstrated that the typical acini from young glands contained numerous protein secretory granules. Ageing was associated with a progressive loss of protein (serous) secretory granules. Furthermore, marked changes and patchy destruction of the endoplasmic reticulum and Golgi apparatus were observed in acini of glands from aged rats when compared to acini of glands from young rats. Measurement of total protein output from acini revealed a significant (Student's t-test, P<0.05) decrease in protein secretion from aged glands compared to glands from young animals. These results suggest that not only is there considerable structural damage, chronic inflammation and mast cell infiltration to the lacrimal gland with ageing, but also possible redifferentiation of acini from serous to seromucous and then to mucous acini. Furthermore, the results also suggest a reduction or an inability of the acini to synthesise and to secrete protein from glands of aged animals compared to glands of young rats. All of these changes appear to occur more rapidly as the rats mature between 20 and 24 months. These findings provide a morphological basis to explain the phenomenon of reduced tear/protein secretion with ageing.

In recent years, the view of the gastric mucosal barrier as a static entity has given way to a dynamic system, the components of which have recently been reviewed in detail. These complex anatomical and physiological properties are conveniently divided into three categories. The major extrinsic factor is the pre-epithelial mucus-bicarbonate barrier, which provides a first line of defence. Intrinsic protection residing with the mucosal cells per se, involves cytoplasmic pH homeostasis together with epithelial restitution and regeneration. Finally, postepithelial factors within the submucosa and interstitium include the microvasculature and maintenance of acid-base balance.<>