Effect of castration and androgen supplementation on sialic acid levels in rat submandibular gland

The effects of castration and testosterone propionate (TP) on rat submandibular gland (SMG) size and sialic acid levels were compared. Castration resulted in a slight decrease in SMG size and a significant reduction in both the whole gland content and concentration of sialic acid. These changes were reversed completely by TP.     

Influence of X-ray irradiation on the ultrastructure of rat submandibular gland striated-duct cells

Previous investigations have indicated that striated-duct cells react to stimulation with an apocrine secretion, morphologically demonstrated by bleb-like projections of the apical cytoplasm. Since bleb formation as an ultrastructural feature also has been debated and sometimes interpreted as a fixation artifact, it was considered essential to extend the studies by exposing the submandibular gland to X rays to establish whether such treatment would have any influence on the formation of blebs. The material used in the present study consisted of rat submandibular glands exposed to X rays in the range of 200-1800 rad. The glands were examined by both SEM and TEM. The duct cells exposed to 200 rad appeared normal, with no sign of alteration in their ability to produce blebs, whereas duct cells exposed to 750 rad showed no sign of bleb formation. Some of the duct cells exposed to 1800 rad showed considerable morphological changes, consistent with oncotic transformation. The results support the conclusion that bleb formation is a normal morphological feature and not an artifact. This study also indicates that the functional activity of the cells is reduced after exposure to X rays.     

Investigation of lipids and lipid metabolism in submandibular salivary gland of the rat

The lipids of rat submandibular salivary gland have been examined at various ages. Phospholipid and cholesterol appear to reach a stable concentration by the third or fourth week of age. No marked changes in the relative amounts of the major phospholipids occurs during the period from 1 week to 3 months of age.

Studies on the in vitro labelling of salivary gland lipid with C¹⁴-tagged glycerol. acetate and mevalonate, and S³⁵-sulphate have shown that these glands have a ready capacity for biogenesis of triglyceride, cholesterol, phospholipid and sulpholipid.     

Effect of chronic constant light on sensitivity of rat submandibular gland

A consistent difference in the secretory response between submandibular (SM) glands of rats maintained under constant light (CL) during 50 days and those of rats under a photoperiod (14 h light: 10 h dark) was found. We have used alpha 1-adrenergic, muscarinic, peptidergic and beta-adrenergic secretagogue agents to study the secretory response of rat SM glands "in vivo". The response to phenylephrine, methacholine and substance P, was increased by exposure CL, while that to isoproterenol was diminished. The changes in the sensitivity of the secretory response from SM gland of rats under CL might be related to changes in the normal interplay of various receptors as well as to possible alteration in the intracellular signal transduction. It may represent and adaptive process of the nervous control of saliva secretion by environmental light and be of physiological and clinical interest.     

Sialographic damage in rat submandibular gland

The damage caused to rat submandibular glands by intraductal injection was examined. When a small volume of isotonic saline was injected, even if salivation was not influenced, salivary composition was greatly affected because the intercellular junctions of the duct cells were damaged. Intraductal injections of hyperosmotic solutions or highly viscous liquids were more effective in damaging intercellular junctions. When interpreting the significance of a salivary composition in clinical diagnosis, it is necessary to consider the sialographic damage which might influence the salivary composition.     

Rat submandibular gland microvasculature following fractionated megavoltage irradiation

A bstract — This study examines the morphological response of the rat submandibular gland microvasculature to radiation in six groups of four rats each. Two groups each received 500, 750, and 1000 rads of megavoltage X-radiation delivered in 250 rad fractions at daily intervals. One group from each dose level was sacrificed 3 days post-irradiation and the other after 14 days and the tissues processed for both light and electron microscopy. At 3 days a mild degree of parenchymal damage, proportional to the total dosage, was present. By 14 days morphological recovery appeared almost complete. Light microscopy showed no obvious vascular changes at 3 days but at 14 days the vessels had become prominent and engorged. Ultrastructural changes at 3 days consisted of marked endothelial cell swelling with small numbers of cells containing large cytoplasmic vacuoles; many caveolae lined the endothelial cell membranes. Cell junctions appeared unaffected although thickening of basement membrane occurred. By 14 days the ultrastructure had returned to normal in the majority of vessels. The microvasculature showed features documented in heart and brain where radiation-induced vasculopathy is of great importance. The distribution of parenchymal damage was restricted to areas apparently supplied by related blood vessels. The vessels in these areas showed a greatly increased capacity for transcellular transport as well as a significant increase in numbers, at least functionally, as recovery occurred.     

Effects of isoflurane on parasympathetic vasodilatation in the rat submandibular gland

Volatile anesthetics have been known to suppress parasympathetic reflex vasodilatation in the lower lip and palate. However, in the submandibular gland, little is known about the effects of these anesthetics on the parasympathetic vasodilatation elicited by reflex and direct (i.e., non-reflex) activation of the parasympathetic vasodilator mechanisms. Although both parasympathetic vasodilatations were inhibited by isoflurane in a concentration- and time-dependent manner, the effects of continuous administration of the alpha(1)-adrenoceptor agonist methoxamine were markedly different: The reflex vasodilatation was not affected by methoxamine, while the direct vasodilatation was significantly reduced. Picrotoxin (GABA(A) receptor antagonist) attenuated the inhibitory effect of isoflurane on direct vasodilatation and the systemic arterial blood pressure. These findings suggest that the isoflurane-induced inhibitory effects on direct vasodilatation are produced by a decrease of peripheral vascular tone by GABAergic mechanisms, whereas those on the reflex vasodilatation are produced exclusively by the inhibition of the reflex center.     

Proteomic analysis of lipopolysaccharide-treated submandibular gland in rat

We investigated changes in the protein profile of submandibular gland (SMG) with inflammation induced by exposure to lipopolysaccharide (LPS) with the aim of identifying potential molecular markers of injured gland. Lipopolysaccharide (2.5μg) was directly administered into rat SMG unilaterally by retrograde ductal injection. At 12hr after treatment, the gland was excised and the proteins identified by two-dimensional difference gel electrophoresis and matrix-assisted laser desorption/ionization-time of flight mass spectrometry. Many proteins in the LPS-treated gland showed a marked change compared to those in the contralateral gland. Of particular note were increases in ubiquitin, a highly-conserved small regulatory protein and in calgranulin B, which has an immunological function in inflammation. Proteins related to apoptosis and stress also showed change in the inflamed gland. The results of this study suggest that the ubiquitin system of protein modification is involved in LPS-induced inflammation in salivary gland, and that a number of specific proteins might be applicable as molecular markers in the monitoring of inflamed or injured gland.     

Radioimmunoassay of rat submandibular salivary gland mucin

A solid phase radioimmunoassay (RIA) for rat submandibular mucin (RSM) was developed and applied to studies of mucin concentration, antigenicity and secretion. The assay utilizes the affinity of 125I-Protein A for IgG to quantitate antigen-antibody immunocomplexes immobilized in the wells of plastic microtitre plates. The technique was highly reproducible and capable of detecting as little as 3 ng mucin protein. The submandibular glands of rats weighing 150-180 g contained 257 micrograms of mucin (dry wt) per mg protein, which is equivalent to about 3.6 mg of mucin per gland. The antiserum to RSM was cross-reactive with mucins from rat sublingual and pig submandibular glands, and rat, human and pig small intestine. No cross-reactivity was detected with mucins from mouse, canine or bovine submandibular glands, and there was no evidence that ABH blood-group sugars contributed to mucin antigenicity. The RIA was used to estimate secretion from dispersed rat submandibular gland cells and gave a more specific and accurate assay of mucin release than previous assays of precursor-labelled radioactive glycoproteins in the culture medium. The beta-adrenergic agonist, isoproterenol, stimulated immunoreactive mucin secretion from cultured cells to approximately twice the level of unstimulated or propranolol-inhibited controls. The RIA appears to offer promising new approaches for studies on mucin metabolism and secretion in health and disease.     

Branched-chain amino acid aminotransferase in submandibular gland of the rat

Crude extracts from submandibular glands of the rat, rabbit, guinea pig and macaque monkey contained high activities of branched-chain amino acid aminotransferase comparable to those from the heart and kidney. In each species, the isoelectric point and relative elution volume on Sephacryl of the aminotransferase from the submandibular gland had the same values as the heart enzyme. The enzyme of rat submandibular gland was partially purified; the properties of the purified enzyme suggest that it is the same type as that from the heart.     

Effects of parasympathectomy on androgen responses of the rat submandibular gland

The effects of androgen on the activities of esteropeptidase and delta 4-3-ketosteroid 5 alpha-reductase were investigated. Ratios of the denervated side to the non-operated side for gland weight and esteropeptidase activity were higher in androgenized females than in untreated females. The specific activities of 5 alpha-reductase were increased by denervation but the total activities were decreased. The results suggest that parasympathectomy leads to higher androgen responsiveness in the rat submandibular gland, which relates to the observed reduction in weight loss of the gland and the increases in its esteropeptidase activities.     

Effect of autonomic nerve stimulation on bleb formation in striated duct cells of the rat submandibular gland

Several previous investigations have shown that blebs form on the apical surface of the striated duct cells of the rat submandibular gland on feeding after starvation. In the present report the influence of autonomic nerve stimulation on bleb formation was studied by electron microscopy. Both parasympathetic and sympathetic stimulation were performed, using electric nerve stimulation. In addition, sympathetic nerve stimulation in combination with alpha- or beta-adrenergic blockers was used. Massive bleb formation took place in response to sympathetic nerve stimulation. This response was almost completely abolished by the administration of alpha- but not by beta-adrenergic blocker. Bleb formation was not seen after parasympathetic nerve stimulation.     

Lumen formation during development of the rat submandibular gland

This study utilized electron microscopy and enzyme histochemistry to examine the morphological steps associated with the formation of a lumen in the end-buds of the embryonic rat submandibular gland. Lumen formation involved the development of junctional complexes by the central cells of the end-buds late on the 16th day of gestation. These junctional complexes established the apical domains of the presecretory cells, and cytofilament aggregates were observed beneath the presumptive luminal plasma membranes. This central area of the end-buds showed strong myosin ATPase activity, presumably associated with the cytofilaments. On the 17th day of gestation, small lumina appeared at the sites delineated by the junctional complexes. The myosin ATPase activity appeared to surround the newly opened lumina. By the 18th day of gestation, microvilli were seen projecting into the lumina, and secretory granules were often visible in the apical cytoplasm near the luminal plasma membranes of the early secretory cells. Myosin ATPase activity was greatly reduced once the lumina had formed.