Secretory activity and the myoepithelial cells of salivary glands after duct ligation in cats

A Ligation of the Lacrimal Excretory Duct in Mouse Induces Lacrimal Gland Inflammation with Proliferative Cells

The lacrimal gland secretes tear fluids to ocular surface, which plays an indispensable role in maintaining the health of the ocular epithelia and protecting the ocular surface from the external environment. The dysfunction of the lacrimal glands causes dry eye disease due to a reduction in tear volume. The dry eye disease is becoming a popular public disease, for the number of patients is increasing, who have subjective symptom and loss of vision, which affect the quality of life. Inflammatory change in the damaged lacrimal gland has been reported; however, a major challenge is to establish a simple animal model to observe the changes. Here, we demonstrated an injury model by ligating the main excretory duct of the lacrimal gland, which is a simple and stable way to clearly understand the mechanism of lacrimal gland inflammation. We observed the process of injury and proliferation of the lacrimal gland and detected a population of lacrimal gland epithelial cells with proliferation potential which were also nestin-positive cells following duct ligation. This study successfully established an injury model to observe the tissue injury process of the lacrimal gland, and this model will be useful for analysis of the inflammation and proliferation mechanism in the future.

Does laser phototherapy influence the proliferation of myoepithelial cells in the salivary gland of hypothyroid rats?

Thyroid hormones influence both development and growth of organs and tissues and guarantee metabolic demands that interfere with the quality of digestive secretions, including those of the salivary glands. Laser phototherapy - LPT can modulate various biological phenomena and its diverse effects permit the action on different cell types. The aim of this study was to evaluate the influence of laser phototherapy on myoepithelial cells of salivary glands of hypothyroid rats. Forty-two albino Wistar rats were divided into two main groups: euthyroid (EU) and hypothyroid (HYPO). Hypothyroidism was induced using propylthiouracil (PTU) for 4weeks. Each group was divided into subgroups: control (without laser) and laser groups (Red/infrared - IR). LPT was used on the submandibular gland and was carried out using a diode laser (λ660 or λ780nm, 40mW, spot size 0.04cm², irradiation area 1cm², 300s, 6J/cm² per gland, 12J/cm² per session) and started two weeks after PTU treatment. LPT was repeated every other day for two weeks. After animal death, the glands were removed, dissected and processed for immunohistochemical analysis. It was observed an increase in the number of myoepithelial cells of hypothyroid control rats in comparison to euthyroid controls (p=0.001). Visible LPT (λ660nm) caused significant higher proliferation of myoepithelial cells in EU rats when compared to IR LPT (λ 780nm)(p≤0.001).It is concluded that, despite the LPT protocol used did not influence myoepithelial proliferation on hypothyroid rats it significantly increased the proliferation on euthyroid animals.

A perspective of comparative salivary and breast pathology. Part I: microstructural aspects, adaptations and cellular events

This is the first part of a review comparing the pathology of salivary and mammary glands. Here, less obvious similarities and differences in functional histology and their influences on pathology are examined with emphasis on myoepithelial cells, stromal components, analogues of mucosa-associated lymphoid tissue, steroid receptors, and intraparenchymal cells of monocytic lineage. Particular cell phenotypes (oncocytic, apocrine, neuroendocrine and clear) are critically evaluated and responses to atrophy, infarction and fine-needle aspiration biopsy procedures are highlighted together with aspects of metaplasia, regeneration, ageing and microcalcification. Areas of controversy or uncertainty which may benefit from further investigations are also discussed.

Early markers of regeneration following ductal ligation in rat submandibular gland

Rat submandibular glands can recover their function and secretory protein content following ductal ligation-induced atrophy. Morphological studies have established that following ligation, deligation of the gland allows the regeneration of new salivary gland tissue. However, little is known about changes happening during early regeneration following intra-oral duct ligation, which does not damage the parasympathetic nerves. Glands that had been 2 weeks ligated or 2 weeks ligated + 3 days deligated were compared. Tissue was prepared for histological, immunohistochemical (SMG-B and Ki-67) and immunocytochemical analyses (smooth muscle actin, aquaporin 5). Haematoxylin and eosin staining of deligated glands showed that some acini regained their cytoplasmic volume; moreover, the loss of Alcian blue/periodic acid-Schiff's staining from the lumen of ducts suggested successful deligation. The deligated gland was characterized by atypical acinar-ductal branched structures, which were less frequent in the ligated gland and rarely seen in normal unoperated tissue. Myoepithelial cells were also investigated since changes in their morphology reflected changes in the acini morphology not readily detected by conventional staining. Actin staining revealed the presence of some shrunken acini in the atrophic tissue, whereas they had regained their normal morphology in the deligated gland suggesting that the acini were recovering. Some acini during deligation regained aquaporin 5 expression, which had decreased during atrophy. SMG-B protein, located in the pro-acinar cell during gland development and usually found in the intercalated duct cells in the adult, was detected in the newly formed acini of the deligated gland. This study suggests that morphological markers of regeneration appear as early as 3 days following ligation removal.

Microenvironmental adaptations in the parotid of ferret investigated by electron microscopy

Previous histochemical investigations suggested that the microenvironment in the parotid of ferret would foster microlithiasis because of a combination of pockets of inefficient secretion, brisk phagy and secretory material rich in calcium. We have undertaken the present ultrastructural investigation in an attempt to provide corroborative evidence. Parotids from four normal ferrets were examined by electron microscopy. Phagosomes in which there was cellular debris and occasionally secretory granules were present in acinar cells, which indicates crinophagy, and residual bodies were present in ductal cells. Atrophic parenchymal cells, degenerate parenchymal cells and apoptotic bodies were present. Cellular debris and secretory material were present in lumina, which indicates stagnation. The results indicate that removal of redundant secretory material and cells and low flow of saliva are features of the parotid of ferret and support the concept of pockets of inefficient secretory activity.

Intraoral duct ligation without inclusion of the parasympathetic nerve supply induces rat submandibular gland atrophy

The atrophic effect of ligating the main duct of the right submandibular gland was examined in rat using a novel intraoral approach that did not include the chorda lingual (CL) nerve. Comparison was made with the effect of duct ligation including the attached CL nerve as carried out in previous studies. In all animals, the contralateral, unligated left submandibular gland was used as a control. At different times (1, 2, 7, 14 and 21 days) after ligation, glands were removed and weighed. Tissue was fixed for morphological analysis and homogenized for biochemical assay of secretory proteins. After 21 days, ligated glands showed a significant decrease in wet weight compared with unligated glands. Weight loss was the greatest (P < 0.05) in glands ligated with the CL nerve included. Light microscopy revealed that following ligation, an initial inflammatory reaction was followed by severe atrophy of acini and granular ducts. The atrophy was less severe when the CL nerve was not ligated. Secretory proteins were decreased from day 1 onwards following duct ligation in both groups. It can be concluded that most of the atrophy induced by duct ligation is independent of damage caused to the parasympathetic nerve supply, although the latter causes a greater atrophy presumably due to denervation.

Biological behavior of myoepithelial cells in the regeneration of rat atrophied sublingual glands following release from duct ligation

The present study aimed to clarify how myoepithelial cells behave during regeneration of an atrophied sublingual gland by investigating cell proliferation and ultrastructure. Atrophy of rat sublingual glands was induced by unilateral ligation of the excretory duct near the hilum with metal clips, which were then removed after one week of ligation for regeneration. The sublingual glands 0-14 days after unligation were examined with single immunohistochemistry for actin as a marker of myoepithelial cells, double immunohistochemistry for actin and proliferating cell nuclear antigen (PCNA) as a marker of proliferating cells, and transmission electron microscopy (TEM). The single immunohistochemistry and TEM showed that myoepithelial cells surrounded residual ducts in the atrophied glands and immature and mature acini in the regenerating glands. Although PCNA-positive myoepithelial cells were identified during regeneration, PCNA labeling indices of myoepithelial cells were low at all time points except at day 7. Ultrastructurally, myoepithelial cells showing bizarre shaped structures in the atrophy changed with maturation of differentiating acinar cells and appeared normal in the regenerated glands. There was no differentiation of the remaining duct cells to myoepithelial cells. These observations suggest that proliferation of myoepithelial cells and differentiation to myoepithelial cells do not commonly participate in the regeneration of atrophied sublingual glands and that the bizarre shaped myoepithelial cells in the atrophied sublingual glands recover the original shapes with acinar cell regeneration.

Regeneration in chronic sialadenitis: an analysis of proliferation and apoptosis based on double immunohistochemical labelling

The understanding of regeneration in salivary glands as a finely tuned balance of cellular proliferation, differentiation and apoptosis has been limited by the difficulty of identifying proliferating cells. This has been overcome in the present investigation by double immunohistochemical labelling for the proliferation-associated antigen Ki67 and for different cell-type-specific antigens applied to 8 specimens of normal parotids and 16 specimens of chronic parotid sialadenitis with particular reference to acini and intercalated ducts. In comparison with low baseline rates of proliferation in normal parotids, proliferative indices were significantly increased in chronic sialadenitis in mature acinar cells, intercalated ductal cells and myoepithelial cells without evidence of proliferation by an additional population of cells. In accordance with findings in glands of experimental animals, the present data do not support the previously postulated concept of regeneration of acini and intercalated ducts by a hypothetical population of uncommitted ductal stem cells. The demonstration of a profound capacity for intrinsic glandular regeneration from differentiated cells represents a biological basis for the good results obtained from conservative therapy of chronic sialadenitis and offers hope for novel therapies designed to reconstitute impaired salivary flow.

Hyperplasia of myoepithelial cells expressing calponin during atrophy of the rat parotid gland induced by duct ligation

The number and location of myoepithelial cells in the rat parotid gland submitted to surgical ligation of its main excretory duct were studied through immunohistochemical labelling for calponin. These cells were labelled by the streptavidin-biotin method using anti-calponin primary antibody, and their number was determined during each step of glandular atrophy, i.e., at time zero (control) and 1, 7, 15, 21, 30 and 60 days after ligation. Morphological analysis showed a gradual decrease and fibrosis of the glandular lobules accompanied by disappearance of the acini and the occurrence of duct-like structures. The expression of calponin was observed in all specimens analysed, being restricted to myoepithelial cells. Labelling revealed the distribution of myoepithelial cells around the acini and intercalated ducts in the control group and around duct-like structures later during the course of atrophy. Quantitative analysis demonstrated significant increase in the number of myoepithelial cells up to day 7 post-ligation, followed by gradual increases which, however, were not statistically significant. These results suggest that myoepithelial cells proliferate intensely up to day 7 post-ligation, an event that coincides with a higher rate of disappearance of acinar cells. After this period, the elevatednumber of cells observed at the end of the previous period is maintained.

Apoptosis and proliferation of myoepithelial cells in atrophic rat submandibular glands

This study was designed to determine whether apoptosis and proliferation of myoepithelial cells occur in atrophic rat submandibular glands. The excretory duct of the right submandibular gland was doubly ligated with metal clips. The atrophic right submandibular glands removed after 1-28 days of duct ligation were investigated using immunohistochemical double staining for actin as a marker for myoepithelial cells and proliferating cell nuclear antigen (PCNA) as a marker for proliferating cells, double staining for actin immunohistochemistry, nick end-labeling (TUNEL) as a marker for apoptotic cells, and transmission electron microscopy (TEM). A few PCNA- and no TUNEL-positive myoepithelial cells were found in the control submandibular glands taken from animals with no operation. In the experimental glands, PCNA-positive myoepithelial cells were common 2 and 3 days after duct ligation and then decreased in number. TUNEL-positive myoepithelial cells appeared at 2 days and were observed most frequently at 5 days. Apoptotic myoepithelial cells were also identified by TEM. These observations suggest that both apoptosis and proliferation of myoepithelial cells occur, especially in the early phase of atrophy, in the rat submandibular gland.

The effects of ductal obstruction on the acinar cells of the parotid of cat

Twenty-nine parotids ligated for between 1 and 365 days were examined by light and electron microscopy. Major changes in the acini were seen at 4 days and included vacuolation, disintegration, extravasation, apoptosis, phagy and a reduction in number and size of secretory granules. There was a further reduction in secretory granules from 7 to 12 days, but acinar cells persisted even up to 365 days, some contained a luminal concentration of small secretory granules and occasionally acinar cells of a similar appearance to normal were found. These findings contrast with a reported absence of acinar cells from the obstructed parotid of rat and show that parotid acinar cells are able to persist and retain an appearance indicative of secretory activity.

Reversible regulation of P2Y(2) nucleotide receptor expression in the duct-ligated rat submandibular gland

Ligation of the main excretory duct of the rat submandibular gland (SMG) produces a pronounced atrophy that is reversed upon ligature removal. Based on previous studies by our group and others suggesting that P2Y(2) nucleotide receptors are upregulated in response to tissue damage, we hypothesized that P2Y(2) receptor activity and mRNA levels would increase after duct ligation and return to control levels after ligature removal. Our results support this hypothesis. Intracellular Ca(2+) mobilization in response to the P2Y(2) receptor agonist UTP in SMG cells was increased significantly after ligation periods of 1.5 to 7 days, whereas no significant response was observed in the contralateral, nonligated gland. P2Y(2) receptor mRNA, as measured by semiquantitative RT-PCR, increased about 15-fold after 3 days of ligation. These increases reverted to control levels by 14 days after ligature removal. In situ hybridization revealed that the changes in P2Y(2) receptor mRNA abundance occurred mostly in acinar cells, which also were more adversely affected by ligation, including an increase in the appearance of apoptotic bodies. These findings support the idea that P2Y(2) receptor upregulation may be an important component of the response to injury in SMG and that recovery of normal physiological function may signal a decreased requirement for P2Y(2) receptors.

Changing myoepithelial cell distribution during regeneration of rat parotid glands

The distribution of the myoepithelial cells during regeneration of the rat parotid gland after atrophy induced by one week of parotid duct ligation was investigated by immunohistochemistry for actin and transmission electron microscopy (TEM). Immunohistochemically, residual ducts were surrounded by actin-positive cells when clips were removed from the duct. Three days later, most of the newly formed acini originating from the residual ducts were also embraced by actin-positive cells. After 10 days, actin-positivity tended to be seen as dots around acini that decreased in number day by day. On day 21 actin-positive cells mainly surrounded intercalated ducts with only a few positive reactions identified at the acinar periphery. Electron microscopically, residual ducts and newly formed acini were peripherally embraced by myoepithelial cells before day 5. After day 7, shift of myoepithelial cells from the periphery of acini to the duct-acinar junctional region was identified. Then few myoepithelial cells were identified at the periphery of acini. These observations indicate that myoepithelial cells migrate from the acinar periphery to the duct-acinar junctional region during rat parotid regeneration, and that such behaviour is closely related to that seen during rat parotid development.

Relation of preoperative sialographic findings with histopathological diagnosis in cases of obstructive sialadenitis of the parotid and submandibular glands: retrospective study

The clinical records, preoperative sialograms and histopathological slides of 33 patients who had been operated on for symptoms of obstructive salivary gland disease were reviewed. Twenty patients had had superficial parotidectomy and 13 excision of the submandibular gland. Among those who had required parotidectomy, preoperative sialograms tended to suggest more architectural damage than was actually noted on definitive histopathological examination. Patients whose symptoms had been present for longer had more severe sialographic and histopathological changes. In the submandibular group, there was a closer relation between sialographic and histopathological changes, and a positive correlation between a short history and the severity of histopathological grading. These differences may reflect the different aetiology and course of obstructive disease in the two types of gland.

Chronic submandibular sialadenitis: ultrastructure and phosphatase histochemistry

Eleven specimens of chronic submandibular sialadenitis were examined. A reduction in secretory material in acinar cells was seen with increasing atrophy until the acini resembled intercalary ducts. Myoepithelial cells and basement membrane were sometimes more conspicuous. Striated ducts showed a reduction of the folding of the plasma membranes in the basal part, and striated and excretory ducts showed a reduction in mitochondria. This possibly represents a functional atrophy secondary to reduced salivary flow. Very atrophic parenchyma largely consisted of simple cells. Phagosomes and apoptotic bodies were occasionally seen, and appear to be involved in the atrophy. Thiamine pyrophosphatase in the Golgi apparatus and acid phosphatase in the GERL were demonstrated in moderately atrophic parenchyma. This is similar to normal and indicates continuing synthetic activity. Acid phosphatase was demonstrated in lysosomes, which appear to be involved in the atrophy by their role in phagy. Alkaline phosphatase was occasionally demonstrated at luminal surfaces, and is likely to be involved in resorption of obstructed luminal contents. The changes are similar to those seen in experimentally obstructed glands and indicate that much of the parenchyma survives by adaptation to the altered environment which forms the basis for the successful results following conservative therapy.

Cell population changes during atrophy and regeneration of rat parotid gland

Limited data exist regarding the changes in number and location of myoepithelial cells during salivary gland atrophy and regeneration. Through the use of double immunohistochemical labeling for muscle-specific actin and amylase coupled with morphometric analysis, this study investigated the changes in distribution and proportion of cell types during salivary gland atrophy/regeneration phases in a model previously used to study proliferation in rat parotid gland. The double immunohistochemical labeling clearly showed the changes in proportion of cell types in the atrophying and regenerating glands. The morphometric analysis showed that the relative myoepithelial area increased (as did the intercalated duct and striated duct areas) as the gland atrophied. Myoepithelial cells occupied 19.0% of the total epithelial area by day 7 of atrophy, up from 2.7% in the resting gland. Regeneration of acinar cells was obvious 1 day after duct release. The myoepithelial cell area decreased to 4.3% of the total epithelial area by day 14 of regeneration; this value was higher than the percentage of area in the resting gland (p = 0.02). The relative areas of acinar, striated duct, and intercalated duct cells returned to resting levels after 14 days of regeneration. The morphometric and histologic results of this study show that the parotid gland is capable of regenerating to essentially normal anatomic condition after 7 days of gland atrophy and then 14 days of regeneration. Each type of cell, however, responded to the atrophy and regeneration differently. Atrophy of salivary glands from radiation therapy. Sjögren's syndrome, or sialadenitis is an important clinical problem. Study of the salivary gland response to atrophy and regeneration may provide a framework for designing strategies for the radioprotection of salivary glands or methods by which to treat or reverse the effects of gland atrophy.

Immunochemical analysis of laminin in duct-ligated submandibular glands of rats

Immunochemical methods have been used to study the expression of laminin during experimental atrophy of the submandibular gland of rats caused by ductal ligation. In normal submandibular glands, laminin immunoreactivity appeared as continuous linear staining around acini and ducts. In the ligated glands, it exhibited an irregular pattern and intensity. Staining was usually stronger around small ducts and acini, which were most prominent in glands ligated for 30 days. Immunoblot analysis showed that the laminin of the rat submandibular gland contains bands that correspond to the EHS alpha 1, beta 1 and gamma 1 chains, and that the composition of the laminin chains does not change during the atrophy.

Expression of collagen and elastic fibers in duct-ligated submandibular glands of mice

Atrophy of salivary glands may occur by ductal obstruction caused by calculus, infection or neoplastic processes, or as consequence of systemic diseases and aging. In the present work, we have used histochemical methods to study the expression of elastic and collagen fibers during experimental atrophy of the submandibular gland of mice. Glandular atrophy was accompanied by a rapid increase in collagen deposition in both septal and intralobular regions. The expression of elastic fibers was not significantly altered during atrophy: a discrete increase of elastic fibers was noted only around ductal structures. The results showed that experimental ductal obstruction is a useful in vivo model to study molecular events that take part in the remodeling of the extracellular matrix during atrophy of salivary glands.

Ultrastructure and three-dimensional imaging of epimyoepithelial islands in benign lymphoepithelial lesions

Benign lymphoepithelial lesions of the salivary glands associated with Sjögren's syndrome are characterized by extensive infiltration of lymphoid cells, atrophy of acini and the presence of so-called epimyoepithelial islands. This report describes ultrastructural and three-dimensional reconstructive studies of epimyoepithelial islands performed at Tokyo Women's Medical College. Ultrastructural examination showed that these islands are composed mainly of epithelial cells containing intermediate filaments and/or tonofilament bundles, scattered lymphocytes and plasma cells. Myoepithelium-like cells containing myofilaments were sometimes found in the peripheral portion of the myoepithelial islands. Also, mitotic figures were rarely found in these islands. Three-dimensional reconstructive study revealed that the epimyoepithelial islands are not isolated cell clusters but are continuous hypertrophic duct-like structures. These results suggest that the epimyoepithelial islands are derived from proliferating duct epithelial cells, especially those of large peripheral ducts.

The effects of obstruction and secretory stimulation on microlithiasis in salivary glands of cat: light and electron microscopy

Obstruction and increased secretory activity are considered to be important aetiological factors of salivary microlithiasis, which may itself be an aetiological factor of sialadenitis. However, there is a lack of substantial evidence for the importance of obstruction, and investigations on increased secretory activity used pathological doses of pharmacological agents. Therefore further investigation of these factors is essential. Feline parotid, submandibular and sublingual salivary glands, in which microliths occur normally as in man, were examined after ductal ligation to produce obstruction, electrical stimulation of the glandular nerves to produce increased secretory activity, or both. Microliths were detected in: 0 out of 38 untreated, 1 out of 55 ligated, 2 out of 17 stimulated and 2 out of 17 stimulated ligated submandibular glands; 6 out of 29 untreated, 7 out of 46 ligated, 3 out of 12 stimulated and 4 out of 14 stimulated ligated sublingual glands; and no parotid glands. The chi 2 test confirmed that the experimental procedures did not produce an increased occurrence of microliths. Microliths were detected in parenchymal cells, intercellularly in atrophic parenchyma, intraluminally, interstitially and in macrophages. The present investigation indicates that obstruction and increased secretory activity are not important aetiological factors of salivary microlithiasis.

Ultrastructural localization of microliths in salivary glands of cat

Although microliths occur in normal human salivary glands and may be an aetiological factor of sialadenitis, little is known of their natural history. In an attempt to remedy this, we investigated a large archival collection of normal and experimental feline parotid, submandibular and sublingual salivary glands. In submandibular and sublingual glands, microliths were detected ultrastructurally in: all types of acinar secretory cells; myoepithelial cells; ductal cells; lumina; intercellular spaces; basement membrane; stroma; macrophages; multinuclear giant cells; and neutrophils. Microliths were not detected ultrastructurally in parotid glands. Microliths appear to form in acinar cells during autophagy and in stagnant secretory material in lumina. Microliths appear to be removed by secretion in the saliva, discharge from cells laterally and basally, and engulfment by macrophages. There appears to be a turnover of microliths, which possibly is upset by secretory inactivity with a resulting accumulation that leads to localized obstruction and sialadenitis.

Analytical ultrastructural investigation of microliths in salivary glands of cat

Microliths in Araldite-embedded pieces of submandibular and sublingual glands of cat were stained in semithin sections by Methylene Blue and Azure II followed by Basic Fuchsin, and were examined in ultrathin sections by electron-microscopical X-ray microanalysis. Calcium and phosphorus were detected in substantial aggregates of crystals that were stained by Basic Fuchsin and appeared to be hydroxyapatite, but were not detected in granular material that was stained by Methylene Blue and Azure II and appeared to be organic. The polychromatic stain thus appears to be a useful indicator of calcified material. The majority of microliths in acini contained substantial aggregates of crystals, whereas the majority of those in ducts did not. This corresponds to the distribution of the glandular calcium, and suggests that microliths are variously enriched with calcium according to its local level.

Immunohistochemical and electronmicroscopic studies of obstructive lesions in submandibular glands

Obstructive sialoadenitis was examined by immunohistochemical techniques for keratin (MoAb KL1, PKK1 and K8.12) and actin. Electronmicroscopy (EMS) was used to identify ultrastructural changes in myoepithelial cells and ductal basal cells. With immunohistochemistry, actin staining was used as a marker of myoepithelium, MoAbs KL1 and PKK1 for ductal luminal cells, and MoAb K8.12 for ductal basal cells. Histologic features of the lesion usually showed degenerative changes of acinar and duct cells with cell infiltration and fibrous replacement. Immunohistochemical findings indicated that actin staining in the changed myoepithelial cells was irregularly positive or negative, and also keratin staining in luminal and ductal basal cells was reduced or disappeared. Ultra-structural features of the changed myoepithelial cells indicated that these cells appeared less altered than adjacent acinar and ductal cells and showed increased amounts of lipid droplets and lipofuscin granules, and also wrinkled processes filled the prominent myofilament material.

Immunoreaction of keratin, actin, S-100 protein and rat-EGF in duct-ligated rat salivary glands

Duct-ligated submandibular and sublingual glands of rats were evaluated immunohistochemically for changes in keratin (MoAb 1164), actin, S-100 protein and rat-EGF (rEGF). Normal salivary glands were reactive for keratin, S-100 protein and rEGF in the granular convoluted tubule (GCT) and duct cells, and for actin in the myoepithelium. Submandibular glands showed a marked reduction of S-100 protein and rEGF staining following duct ligation, and no increased staining of proliferating epithelial cells of the late stage in duct ligated glands. Sublingual glands revealed no marked changes for actin staining in myoepithelial cells, irrespective of atrophic changes occurring in acinar and duct cells after duct ligation. Immunohistochemical patterns differed for each type of gland; changes associated with the obstructive lesion were more prominent in the submandibular gland.

The effects of a liquid diet on initial and sustained, stimulated parotid salivary secretion and on parotid structure in the rat

Adult male rats were maintained on a nutritionally adequate liquid diet, or laboratory chow and water (controls), for 7 days. They were then anaesthetized and parotid flow was recorded after isoprenaline or pilocarpine stimulation, each collected over two, timed sampling periods--an initial 5 min and a subsequent 15 min. The isoprenaline-induced flow rates in liquid diet rats were reduced to 45 and 30% of those in control rats for the first and subsequent samples respectively (p less than 0.02). After pilocarpine stimulation there were no significant differences in the first samples, but in the subsequent samples the flow rate in liquid diet rats was reduced to 54% of that in controls (p less than 0.001). The parotid gland weights were reduced by 35% in liquid diet rats compared to controls (p less than 0.05). On computerized planimetric analysis, parotids (from rats that had not been given secretagogues) had significantly smaller mean acinar areas, mean acinar profile perimeters and mean acinar transection diameters after liquid feeding (p less than 0.001). The findings support the notion that there is a functional reserve capacity available in atrophied glands to support the relatively fast flow that occurs on initial stimulation but which becomes exhausted during sustained stimulation. This exhaustion occurs more severely and more rapidly in the low-volume, protein-rich saliva elicited by sympathomimetic stimulation than in the high-volume, low-protein saliva formed in response to parasympathomimetic stimulation.

Chloride handling by submandibular cells from young and old rats with and without duct ligation

To examine the relation between structure and function in aging salivary glands, we have studied the duct-ligated submandibular gland of rats. Following 5-8 days ligation, glands from young (7-8 months) and old (21-23 months) rats exhibited approximately 90% loss in proportional volume of acinar cells. Most remaining epithelium was highly abnormal. No significant differences were detected in the ability of cells prepared from young and old animals, either control or ligated, to flux 36Cl-. Both basal uptake and muscarinic-cholinergic stimulated release were comparable.

Sialographic images of pathological changes in the mouse parotid gland

In order to correlate pathological changes of mouse parotid glands with their sialographic images, we conducted studies on mice with known pathological changes: mice with Stensen's duct ligated, NZB mice with a systemic auto-immune disease, and aged mice. The sialographic images were found to be specific for the pathological changes: The glands after ligation of Stensen's duct were characterized by dilated, large excretory ducts with a reduced system of peripheral ducts; the glands of NZB mice showed lobular leakage of the contrast medium from small excretory ducts; and the glands of aged mice showed a great reduction in the ductal system. It is concluded that sialography yields useful information on the pathological changes of the ductal systems in the mouse parotid gland.

Chronic sialadenitis. An immunocytochemical study in humans

The cellular changes in salivary gland parenchyma with chronic inflammation were studied immunocytochemically with a panel of antibodies. Myoepithelial cells were labelled with antimyosin, duct cells with a polyclonal anti-callus prekeratin, a monoclonal anti-keratin CAM 5.2 and a monoclonal anti-keratin 7 (RPN 1162), and a subpopulation of basal duct cells with a monoclonal anti-keratin 16a. The wide range of changes observed were similar to those described following experimental duct ligation. One of the most striking features was the survival of myoepithelial cells surrounding persisting acini and ductal structures. Most of these ductal structures appeared to be either surviving intercalated ducts or were altered acinar cells. There was no evidence of myoepithelial or ductal hyperplasia. The 16a positive basally located duct cells which are conspicuous in normal glands, pleomorphic adenomas and in the epithelial islands in lymphoepithelial lesions (Palmer et al. 1985; 1986) were virtually absent, except in one specimen with mild inflammatory changes. If this cell type represents a reserve cell, then loss of it may preclude recovery of the remaining parenchyma following resolution of inflammation.

The myoepithelial cell: embryology, function, and proliferative aspects

Myoepithelial cells form an integral part of the secretory and ductular portion of most glands. They share a common origin with lumenal epithelial cells and influence proliferation and differentiation of developing terminal glandular buds by producing a scaffold of basement membrane proteins. Their contractile capacity, controlled by hormonal and neural mechanisms, plays an important role in propulsion of secretions. Furthermore, myoepithelial cells maintain glandular structural integrity and transport metabolites to secretory cells. The advent of modern immunochemistry made identification of specific myoepithelial cell markers possible which facilitated studies on their presence and behavior in disease processes. Although the significance of many myoepithelial alterations is speculative, some have proved valuable in determining the histogenesis of glandular lesions.

Effect of duct ligation on amylase release from rat parotid slices

The effect of parotid duct ligation on amylase release from the rat parotid gland by isoproterenol was investigated in vitro. Unilateral ligation of the excretory duct progressively reduced amylase activity in the medium (the released amylase activity), but did not change the percentage of amylase release. Amylase activity in the parotid tissue decreased progressively after duct ligation, and the decrease rates of the amylase activity were very similar to that of the released amylase activity. Accordingly, the decrease of the released amylase activity after the ligation may be not due to an alteration in the amylase release mechanism, but due to the decrease of amylase content in the parotid tissue.

Epimyoepithelial' islands in lymphoepithelial lesions. An immunocytochemical study

A panel of antibodies has been used in an immunoenzyme study in an attempt to characterize the cell types found in the 'epimyoepithelial' islands of lymphoepithelial lesions. Myoepithelial cells, which can be specifically stained with an anti-smooth muscle antibody were not found. The majority of cells stained with anti-prekeratin, suggesting a duct cell differentiation. A subpopulation of duct cells stainable with a monoclonal antikeratin (16a), previously described as occupying a basal location in normal salivary gland ducts, was clearly demonstrated. It is suggested that these cells may be important in the epithelial proliferation in these islands. The hyaline material within and surrounding the epithelial islands was positive for type IV collagen and therefore consists of basement membrane material.

Immunohistochemical observation of EGF and NGF in submandibular glands after duct ligation with or without testosterone administration

Immunohistochemical detection of epidermal growth factor (EGF) and nerve growth factor (NGF) was carried out in duct-ligated submandibular glands (SMG) of mice with or without testosterone treatment. High levels of EGF and NGF were limited to granular convoluted tubule (GCT) cells in normal adult male mice, and reduced levels were evident in the female. After duct ligation, EGF and NGF stainings began to decrease on the 2nd or 3rd day, and by the 10th day, no staining was detectable. Decreasing levels of EGF and NGF following duct ligation, were more pronounced in the male SMG than in the female. Testosterone administration before ligation resulted in decreased EGF and NGF levels of staining; however, staining of sections on the 1st and 3rd day was a little stronger than comparable stained sections of untreated mice. In contrast, testosterone administration after duct ligation showed GCT cells of normal size with some degranulation at 10 days and irregular staining of growth factors with varying degrees of degranulation at 14 days. Histochemical staining for EGF and NGF in this group was marked, as in the normal, until the 10th day with decreasing reactions by the 14th day.

Progressive secretory dysfunction in the rat submandibular gland after excretory duct ligation

Unilateral ligation of the main excretory duct of the rat submandibular gland caused a progressive deterioration of secretory function characterized by: (1) the secretion of progressively smaller volumes of saliva in response to a standard maximal intraperitoneal (i.p.) dose of pilocarpine. Saliva volume was reduced 69.4, 88.8 and 95.9 per cent, respectively, 1, 3 and 7 days after duct ligation. By 2 weeks, the contralateral, non-ligated gland had an enhanced response to pilocarpine and the ligated gland a 96.8 per cent reduction in the volume of saliva secreted; (2) a progressive reduction in the maximum flow rates attained upon stimulation with pilocarpine, which were 23.4, 10.1 and 5.1 per cent of those attained in the contralateral gland at, respectively, 1, 3 and 7 days after ligation; (3) a progressive increase in the sodium concentrations of saliva, which became plasma-like 2 weeks after ligation; (4) a significantly reduced secretory response to standard doses of isoproterenol, phenylephrine, methoxamine and substance P 2 weeks after ligation. In addition, both cholinergic and adrenergic receptors were significantly reduced in number 2 weeks after ligation. Administration of daily injections of pilocarpine (10 mg, i.p.) after duct ligation reduced the gland atrophy observed 3 days (by 17 per cent) and 1 week (by 9 per cent) later, but did not prevent the reduction in volume or flow rats observed after duct ligation alone. Thus ligation of the main excretory duct causes a progressive dysfunction in acinar and duct cells in the rat submandibular gland and alters their responsiveness to physiological regulators of secretion. The alterations in glandular secretory function and in the composition of saliva which occur in diseases causing partial or complete obstruction to the flow of saliva are likely to be similar to the changes described.

Effects of duct ligation on choline acetyltransferase activity in salivary glands of rats

Duct ligation was found to cause a decrease in the weights of submaxillary and parotid glands examined 3 weeks postoperatively. Choline acetyltransferase activity in ligated glands was compared with that in unligated contralateral glands. The enzyme activity was also measured in the glands from both sides of unoperated control animals. Interference in the assay of choline acetyltransferase by other acetylated compounds was avoided by introducing suitable control incubations. Ligated submaxillary glands showed a small decrease in the activity of choline acetyltransferase both when compared with contralateral glands and with glands of control rats. In parotid glands the enzyme activity was found to be lower only when ligated and contralateral glands were compared. Structural changes in the nerves and reduced traffic of impulses in them may have to be considered as explanations for the reduction in enzyme activity in duct-ligated glands.

Histological effects of ductal ligation of salivary glands of the cat

Forty-two submandibular, 32 sublingual and 31 parotid glands have been examined microscopically after ductal ligation avoiding the nerves for periods from 1 day to 1 yr. After an initial increase in size, there was over-all atrophy in all three glands. In the parotid gland the response was uniform and there was progressive atrophy until most of the acini were extremely atrophic. However, in the submandibular and sublingual glands the response was very variable, and although in some glands most of the acini were extremely atrophic, in other glands there was far less atrophy and most of the remaining acini appeared more or less similar to normal despite prolonged ligation. These results contrast with those of earlier experimental studies on ductal ligation, but have similarities with observations on the behaviour of human salivary glands.

Motor and secretory effects of nerves on the parotid gland of rat

The influence of parasympathetic and sympathetic nerves on the parotid gland of the rat was investigated. It was found that both divisions of the autonomic nerves evoke secretion and probably also motor effects in this gland. Secretion elicited on sympathetic stimulation was mediated both via alpha- and beta-adrenoceptors, while motor effects were mediated via alpha-adrenoceptors. On stimulation of the autonomic nerves a lower duct pressure was reached in the parotid than in the submaxillary gland, and on sympathetic nerve stimulation the flow of saliva always started later from the parotid than the submaxillary gland. These findings are discussed in the view of the different arrangement of the myoepithelial cells in the 2 glands.

Surgical elimination of drooling

Drooling involves great practical problems in the care of patients with cerebral paralysis and mental deficiency. Different types of medical and surgical treatments have been used. In 17 disabled patients chorda tympani has been cut bilaterally in order to reduce the production of saliva, especially from the submandibular and sublingual glands. The loss of taste on the anterior part of the tongue seems to contribute to the reduction of salivation. Fifteen patients have been observed postoperatively during two to four years. Five patients have been cured, two are considerably improved and seven partially improved. The effect of nerve section was illustrated by Tcm99 scintigraphy in two additional cases before operation and six months postoperatively. No complications were observed.

The effects of ductal ligation on the parenchyma of salivary glands of cat studied by enzyme histochemical methods

Submandibular, sublingual and parotid glands of cat have been studied following periods of ductal ligation ranging from 1 day to 1 year. An increased prominence of granules of acid phosphatase, beta-glucuronidase and E600-resistant esterase reaction products was sometimes seen in acinar cells and atropic striated ductal cells, and probably represents increased lysosomal enzymic activity, which may be of importance in the adapation of the parenchyma to the altered environment. Other reaction products often appeared to be at normal levels in parenchymal structures that were not very atrophic, and at reduced levels in those that were very atrophic, suggesting a reduction of functional activity in these structures.

[Morphology of salivary gland diseases]

The human salivary glands represent a functional system with manifold responsibilities and interactions to the organism. The major and minor salivary glands show a common construction schedule consisting of an acinar functional system for the production of an enzyme- and mucin-containing primary saliva and a ductal functional system with manifold secretory, resorptive and regulatory responsibilities for the transport and the definitive composition of the saliva. The cyclic AMP and calcium iones localized in the glandular acini have an exceptional importance for the course of the secretory process. The neurohormonal control of the salivary secretion results by adrenergic and cholinergic transmitter substances. Moreover the secretory process shows a daily cycle combined with morphological alterations of the glandular cells (so called circadian structures). The fluid secretion of the salivary duct system (the output of sodium-, potassium- and chlorine-iones) represents an active energy-consumed transport process which will be regulated by several factors (autonomic nervous system, quantity of perfusion, hydrostatic pressure in the blood capillaries, transepithelial active transport by ATP-consumed pump systems). The striated ducts are the functional most important sector of the duct system for a rapid fluid- and electrolyte excretion. The terminal axons of the postganglionic sympathic and parasympathic neurits are characterized by spindle-shaped enlargements (varicosities) which contain neurosecretory granules. In the region of the acinar and intercalated duct cells a direct synaptic contact exists for the stimulation transmission, in the course of which the terminal axon contacts immediately with the effector cell by penetration of the basement membrane. The salivary glands form a part of the stabil tissues with reversible postmitotic cells in regard of the tissue regeneration. Under pathological conditions (inflammations, impediment of secretion fluid, radiation effects etc.) metaplasias and proliferations of the duct system arise with development of indifferent duct formations analogous to the type of an embryonal salivary gland. The terminal zone between intercalated and striated ducts represents an indifferent zone with large regeneratory potency. A special behaviour shows the myoepithelial cells which are developed as well to the outside of primitive embryonic duct buds as differentiated intercalated and striated ducts. Morphologically three types of diseases can be classified in the salivary glands: sialadenosis, sialadenitis and tumours.(ABSTRACT TRUNCATED AT 400 WORDS)