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    Histochemical studies of the secretory processes in bovine salivary glands : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science at Massey University /
    (Massey University, 1981) Birtles, Mervyn John
    Salivary glands from 12 bovine animals were dissected, weighed and sampled for histological examination. The total salivary gland weight was positively correlated with body weight but there were not normally consistent differences between the weights of left and right glands. However, in animals that had chronic re-entrant cannulations of the left parotid and mandibular ducts, the ipsilateral glands were always lighter. The histological features of salivary glands and the histochemical reactivity of their secretory and duct cells were examined. Parotid gland secretory endpieces were elongated and their individual cells contained PAS+ve granules. These cells were shown by immunohistochemistry to be the site of protein secretion and thus were classified as proteoserous cells. Chronic parotid duct cannulation in association with duct obstruction caused dilation of the secretory endpiece lumens and degenerative changes within the endpiece cells. Intralobular duct cells contained PAS+ve granules which may be the secretory component that is associated with secretory IgA. Variable numbers of intrastriated duct cells occured in the parotid glands of different animals and in retrospect, this was found to correlate positively with the animals known susceptibility to bloat. The parotid excretory duct contained many goblet cells which contribute a small amount of mucosubstance to the proteoserous secretion. Secretory endpieces of the mandibular gland were composed of mucous cells which were PAS, AY and weakly AB+ve and demilune cells which were PAS and AB+ve as well as acidophilic and pyroninophilic. Clumps of plasma cells were observed in the intralobular connective tissue. The effect of obstruction of chronic duct cannulation on the mandibular gland was to dilate endpiece and intralobular duct lumens, cause degenerative changes in mucous and demilune cells and increase the numbers of small lymphocytes, PMN neutrophils and mast cells in the connective tissues of the gland. By contrast with the excretory duct of the parotid, that of the mandibular contained no goblet cells but simply a stratified columnar epithelium. Mucous cells of the sublingual gland were PAS+ve, AY+ve and weakly AB+ve and arranged into long tubular endpieces. The demilune cells contained abundant PAS+ve, AB+ve, AY-ve granules. Many plasma cells were present in the connective tissue between the secretory endpieces and around the intralobular and interlobular ducts. In animals with chronic cannulations of parotid and mandibular glands the ispilateral sublingual gland weighed less than the contralateral gland. The posterior tongue, soft palate, pharynx and the lingual aspect of the epiglottis contained extensive areas of glandular tissue. The secretory endpieces consisted of a high proportion of mucous cells and a few scattered proteoserous demilune cells. The glandular tissue of the epiglottis contained abundant plasma cells in the intralobular connective tissue. Based on their histochemical reactivity the demilune cells of the intermediate buccal glands produced a purely serous secretion. In addition, the intermediate and dorsal buccal glands contained many AB, AY and PAS+ve mucous producing cells. The labial glands were small, scattered lobules of secretory tissue found at the labial commisures. The glandular lobules were composed of tubular secretory endpieces capped with large proteoserous demilune cells which were AY-ve, PAS+ve, strongly acidophilic and pyroninophilic. Large numbers of plasma cells were found in the connective tissues within and around the secretory tissue.
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    A histochemical study of bovine salivary gland secretory products and an investigation of intraepithelial granular duct cells of the parotid gland : a thesis presented in partial fulfillment of the requirements for the degree of Master of Philosophy in Physiology and Anatomy at Massey University
    (Massey University, 1983) Gurusinghe, Chandan Jayaraj
    Paraffin wax embedded histological tissue samples of bovine salivary glands were examined by staining, histochemical and immunohistochemical methods. The characteristically tubular secretory endpieces were composed of either proteoserous cells or mucous cells and demilunes. Parotid glands and the histologically identical ventral buccal glands were composed entirely of proteoserous cells which occasionally contained diastase resistant PAS positive neutral glycoproteins, additionally confirmed by acetylation and saponification. Immunohistochemical studies established that most proteoserous cells also contained either protein band 4 or band 10. An examination of sheep and cattle parotid glands revealed that basal striations were absent from intralobular ducts of cattle but were abundant in those of sheep. Some duct cells contained diastase labile and diastase resistant PAS positive material and apical blebs. A granulated intraepithelial cell type, which was ultrastructurally examined and found to be similar to a globule leucocyte, was specific to intralobular duct walls of the parotid glands; their precise function was not established. The main excretory duct of the parotid gland contained several goblet cells. The mandibular gland mucous cells contained acidic and neutral mucosubstances. The presence of acidic groups was confirmed by methylation, saponification and neuraminidase digestion. The conspicuous demilunes contained acidic and neutral mucosubstances and acidophil granules which contained protein band 8. Intralobular ducts with tall columnar cells were basally striated. Goblet cells were not identified in the main excretory duct. The sublingual gland mucous cells contained neutral and acidic mucosubstances; the latter were not neuraminidase labile. Unlike the mandibular glands, the sublingual mucous cells stained for sulphate goups, attributed to sulphated or sialo-sulphated glycoproteins, since hyaluronidase digestion did not eliminate basophilia at low pH. The demilune cells were mostly proteoserous and contained protein band 9. The "striated" intralobular ducts were identical to those of the mandibular gland. Intermediate buccal, dorsal buccal, palatine, posterior tongue and pharyngeal glands mucous cell histochemical composition was similar to those of the sublingual glands. The demilune contents of the minor glands were mainly proteoserous; however those of the pharyngeal and posterior tongue occasionally contained acidic and neutral mucosubstances. Two unusual features of the minor glands were the presence of goblet cells in intralobular ducts of the pharyngeal glands and the appearance of an atypical secretory mechanism in dorsal buccal, intermediate buccal and palatine glands, the secretions of which frequently contained cellular debris mixed with mucus. Humoral immunity in bovine salivary glands was mediate by sublingual, mandibular and pharyngeal glands, three glands which contained abundant subepithelial plasma cells The parotid and ventral buccal glands noticeably lacked plasma cells but contained intraepithelial granular duct cells. It was proposed that these cells may provide cell-mediated immunoprotection against bloat since increased numbers of these cells have been reported in animals with low bloat scores. Salivary protein band 4 from parotid saliva has been correlated with bloat susceptibility in cattle, but was equally distributed in parotid tissues of both low and high bloat susceptible animals, suggesting that band 4 is synthesised but not secreted by low bloat strains.
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    A study of morphological and physiological changes in the mandibular gland of the sheep associated with eating and direct stimulation : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University
    (Massey University, 1981) Ariyakulkaln, Punnipa
    This study was undertaken to investigate relationships between the structure of the mandibular gland of the sheep and its secretory activity in response to feeding, direct stimulation of autonomic nerves, or pharmacological agents that mimic the action of autonomic transmitters. Forty-five crossbred Romney ewes and wethers were used in acute experiments and twenty-two in chronic experiments. Histochemical and electron microscopical examinations of the structure of mandibular glands confirmed that their secretory endpieces are composed of mucous tubulo-acinar cells and seromucous demilunes. The mucous acini contained a single type of electron lucent granules, whereas the granules of demilunes typically exhibited a tripartite structure. The intercalated ducts were relatively short and lined by non-secretory, simple cuboidal cells and occasional basal cells. Striated ducts were numerous and lined by four cell types, the most common of which (type-I) were tall, columnar, electron lucent cells with well developed membrane infoldings basally with associated mitochondria and small, dense, apical bodies. Myoepithelial cells were distributed densely around the secretory endpieces and within the basement membranes. Myoepithelial cells were also found embracing the intercalated duct cells. Both AChE-positive and biogenic-amine fluorescent nerve fibres were present around the secretory endpieces and the walls of blood vessels. Fewer biogenic-amine fluorescent fibres were seen in relation to duct cells. Electron microscopy showed unmyelinated fibres in both epilemmal and hypolemmal sites. The epilemmal axons were frequently found close to a variety of effector cells, while hypolemmal axons were observed occasionally in the intercellular space between adjacent striated duct cells and between intercalated duct and mucous cells. Axons containing large granular vesicles were also found within interstitial nerve bundles. Mandibular secretion was studied after cannulation of the mandibular duct in both acute and chronic experiments. In anaesthetized animals, stimulation of either the chorda lingual nerve (3-8V, 5-10Hz, 0.2 msec) or injection of carbachol (40 µg kg-1 body weight, iv) within 10-25 sec caused a copious secretion (0.33-0.74 g min-1) of low protein content (0.44-1.56 mg ml-1). This response was completely blocked by atropine (0.1 mg kg-1 body weight). In contrast, stimulation of cervical sympathetic trunk (3-8V, 5-10 Hz, 0.2 msec) after a latency of 35-102 sec caused a meagre secretion (0.01-0.06 g min-1) of high protein concentration (4.02-25.68 mg ml-1). Isoprenaline had similar effects. Secretory responses to sympathetic stimulation were blocked by propranolol (1.0 mg kg-1 body weight). Studies involving gel electrophoresis demonstrated major protein bands exclusively in the sympathetic nerve or isoprenaline stimulated saliva. These major protein components (both soluble and insoluble) were found by immunocytochemical studies to be localized in the demilunes and some striated duct cells of the resting gland. It was found that in sheep fed lucerne chaff (ca. 1,000 g daily) a rapid and sustained mandibular flow only occurred during eating, although, short term increases were seen, for example, during drinking. Flow was absent during rumination and slight (0.95 ± 0.09 g h-1) or absent at rest. Saliva produced during eating had its highest protein concentration almost immediately as eating commenced (1.65 ± 0.06 mg ml-1) and remained at a high level during the first hour of eating (1.55 ± 0.06 mg ml-1) Propranolol (1.0 mg kg-1 body weight, iv) caused significant reductions in protein secretion during eating (P<.001) without associated changes in flow. Gel electrophoretic studies confirmed the presence of a major protein band similar to soluble protein band X found in sympathetically evoked saliva. The intensity of this major protein band in saliva collected during eating was also reduced after propranolol treatment. Saliva collected during teasing had a high protein concentration (2.73 ± 0.20 mg ml-1). It is concluded that sympathetic activation was involved mainly early in the eating period and that parasympathetic nerves were active throughout. The latter was confirmed by a great reduction in flow after injection of atropine (0.1 mg kg-1, iv). Morphological studies of the glands of sheep whose food had been withheld for 20 hours revealed that both the mucous acini and seromucous demilunes were filled with secretory granules. Stimulation of the chorda lingual nerve for 2-4 hours caused acini to discharge their contents of secretory granules, but no appreciable changes in the demilunes. On the other hand, stimulation of the cervical sympathetic trunk produced varying degrees of degranulation in the demilunes, with, in some cells, vacuolation. Infusion of isoprenaline (2h; 0.3 µg kg-1 min-1) produced similar changes in demilunes. Striated duct cells showed reduced PAS-staining, and disruption of their basal regions, particularly after stimulation of sympathetic nerves. Concurrent stimulation of both sympathetic and parasympathetic nerves resulted in a combination of the above separate effects. Eating led to extensive degranulation and greater evidence of synthesis in the mucous acini than parasympathetic nerve stimulation, the changes increasing with the duration of eating, and a depletion of secretory granules in demilunes that could be prevented by propranolol. (1.2 mg kg-1 body weight, iv ). The morphological changes in demilunes were not proportional to the duration of eating but were greatest in its early phases. Evidence of small dense bodies which were apparently discharged via the apical membrane of striated duct cells and a loss of PAS-staining in these cells suggest that they secrete during eating. However, neither damage to striated duct cells nor secretory endpieces was evident. The results suggest that the sheep mandibular gland is naturally stimulated by both divisions of the autonomic nervous system, with acinar cells predominantly under the parasympathetic and demilunes under the sympathetic control. The sympathetic stimulation of salivary protein secretion appears to be mainly mediated via a β-adrenergic mechanism whereas the secretion of fluid and probably also mucus glycoproteins is an atropine-sensitive parasympathetic effect. On both morphological and physiological grounds it is suggested that in sheep mandibular glands, myoepithelial cell contraction is important in assisting the secretion of viscous saliva. Further studies on the following areas would seem appropriate: (i) systematic morphological studies using stereological analysis of changes in the acinar cells, demilunes, striated ducts and their cytoplasmic components; (ii) ultrastructural examinations of the innervation pattern in this gland under normal conditions, after specific denervation and reinnervation; (iii) studies of the nature and origin of the salivary proteins secreted during eating and nerve stimulation and (iv) the use of chronically cannulated animals for studies of the influence of different conditions of feeding.