Ultrastructural studies of the rat submandibular gland in streptozotocin induced diabetes mellitus

Autologous mesenchymal stem cells offer a new paradigm for salivary gland regeneration

Salivary gland (SG) dysfunction, due to radiotherapy, disease, or aging, is a clinical manifestation that has the potential to cause severe oral and/or systemic diseases and compromise quality of life. Currently, the standard-of-care for this condition remains palliative. A variety of approaches have been employed to restore saliva production, but they have largely failed due to damage to both secretory cells and the extracellular matrix (niche). Transplantation of allogeneic cells from healthy donors has been suggested as a potential solution, but no definitive population of SG stem cells, capable of regenerating the gland, has been identified. Alternatively, mesenchymal stem cells (MSCs) are abundant, well characterized, and during SG development/homeostasis engage in signaling crosstalk with the SG epithelium. Further, the trans-differentiation potential of these cells and their ability to regenerate SG tissues have been demonstrated. However, recent findings suggest that the "immuno-privileged" status of allogeneic adult MSCs may not reflect their status post-transplantation. In contrast, autologous MSCs can be recovered from healthy tissues and do not present a challenge to the recipient's immune system. With recent advances in our ability to expand MSCs in vitro on tissue-specific matrices, autologous MSCs may offer a new therapeutic paradigm for restoration of SG function.

Early effect of laser irradiation in signaling pathways of diabetic rat submandibular salivary glands

Low-power laser irradiation (LPLI) is clinically used to modulate inflammation, proliferation and apoptosis. However, its molecular mechanisms are still not fully understood. This study aimed to describe the effects of LPLI upon inflammatory, apoptotic and proliferation markers in submandibular salivary glands (SMGs) in an experimental model of chronic disorder, 24h after one time irradiation. Diabetes was induced in rats by the injection of streptozotocin. After 29 days, these animals were treated with LPLI in the SMG area, and euthanized 24h after this irradiation. Treatment with LPLI significantly decreased diabetes-induced high mobility group box 1 (HMGB1) and tumor necrosis factor alpha (TNF-α) expression, while enhancing the activation of the transcriptional factor cAMP response element binding (CREB) protein. LPLI also reduced the expression of bax, a mitochondrial apoptotic marker, favoring the cell survival. These findings suggest that LPLI can hamper the state of chronic inflammation and favor homeostasis in diabetic rats SMGs.

Morphology of the intralobular duct of the submandibular gland in rats in case of experimental diabetes mellitus

The objective of study is to study the peculiarities of morphological changes in different subdivisions of the intralobular duct of the submandibular gland (SMG) in rats in case of experimental diabetes mellitus (DM). The study included sexually mature male Wistar rats. Experimental DM was induced by streptozotocin. Electron microscopic study of subdivisions of the intralobular duct of the SMG was carried out on the 14th, 28th, 42nd, 56th, and 70th days of the experiment. In early stages of experimental DM the intercalated ducts are characterized by a relatively unchanged structure, and in late stages vacuolization of the cytoplasm of their epithelial cells is observed. Since the 14th day vacuolization of mitochondria is observed in epithelial cells of the granular ducts being the most pronounced on the 28th day and not apparent over the subsequent periods. The degree of filling with granules reduces till 56th day, however, it increases sligthly on the last day of the experiment. On the 28th-70th days vacuolization of the cytoplasm is observed in epithelial cells of the striated ducts. In addition, on the 14th day the mitochondrial matrix of these cells condenses; over the next periods it becomes enlightened and mitochondrial cristae are clearly visualized and disorganized.

CONCLUSION

In the intralobular duct of the SMG in experimental DM dystrophic changes of different intensity occur in the granular and striated ducts on the 14th day and in the intercalated ducts only since the 42nd day of the experiment.

Effects of Diabetes on Post-Menopausal Rat Submandibular Glands: A Histopathological and Stereological Examination

OBJECTIVE

The menopause in elderly women is a physiological process where ovarian and uterine cycles end. Diabetes means higher blood glucose level that is a metabolic disease and has an increased incidence. The aim of the study was to examine the single or combined effects of menopause and diabetes that causes pathophysiological processes on submandibular gland on ovariectomy and diabetes induced rat models.

MATERIALS AND METHODS

Sprague Dawley twelve weeks old female (n=24) rats were divided randomly into four groups; Healthy control group (n=6), diabetic group (DM, n=6), ovariectomized group (OVX, n=6), post ovariectomy diabetes induced group (DM+OVX, n=6) individually. Histopathological, histochemical and stereological analyses were done in these groups.

RESULTS

Significant neutrophil cell infiltrations and myoepithelial cell proliferations, granular duct and seromucous acini damages and changes in the content of especially seromucous acini secretion in DM and/or OVX groups and distinctive interstitial and striated duct damages in post ovariectomy diabetes induced group were detected. Alterations ingranular ducts hypertrophic and in seromucous acini atrophic were determined in DM and/or OVX groups.

CONCLUSION

The results revealed the pathophysiological processes that lead to morphological and functional alterations on the cellular level in submandibular glands. The molecular mechanisms related with pathogenesis of diabetes and menopause need further investigation.

iTRAQ-based quantitative proteomic analysis of submandibular glands from rats with STZ-induced hyperglycemia

The impairment of salivary glands activity is often connected to the complaints of dry-mouth and subsequent degradation of the periodontium of diabetic patients. In this context, submandibular glands (SMGs) play a central role in saliva production and so the understanding of the molecular pathways affected is of paramount importance. Using a streptozotocin-induced hyperglycemia rat model and two different time points (2 and 4 months), we applied mass spectrometry-based proteomic techniques, validated with standard western blot analysis, to identify and quantify the effect of chronic hyperglycemia on the proteome of SMGs. We observed significant variations of proteins such as kallikreins, protein S100A6 or annexins. After 2 months of hyperglycemia, we observed an early phase response characterized by a significant increase of protein S100A6, linked to the inflammatory response, together with the impairment of metabolic and energy production processes. On the other hand, vesicular transport appeared to be favoured in such conditions. Interestingly, in a long-term response to hyperglycemia after 4 months of exposure, we observed a general attenuation of the variations. In conclusion, we present data that support the existence of an adaptation of the gland to long-term stress.

Hyperglycemia and xerostomia are key determinants of tooth decay in type 1 diabetic mice

Insulin-dependent type 1 diabetes mellitus (DM) and oral diseases are closely interrelated. Poor metabolic control in diabetics is associated with a high risk of gingivitis, periodontitis and tooth loss. Salivary flow declines in diabetics and patients suffer from xerostomia. Reduced saliva predisposes to enamel hypomineralization and caries formation; however, the mechanisms that initiate and lead to progression of tooth decay and periodontitis in type 1 DM have not been explored. To address this issue, we analyzed tooth morphology in Akita ⁻/⁻ mice that harbor a point mutation in the Ins2 insulin gene, which leads to progressive hyperglycemia. Mandibles from Akita ⁻/⁻ and wild-type littermates were analyzed by microCT, scanning EM and histology; teeth were examined for amelogenin (Amel) and ameloblastin (Ambn) expression. Mice were injected with pilocarpine to assess saliva production. As hyperglycemia may alter pulp repair, the effect of high glucose levels on the proliferation/differentiation of cultured MD10-F2 pulp cells was also analyzed. Results showed that Akita ⁻/⁻ mice at 6 weeks of age showed chalky white incisors that correlated with marked hyperglycemia and impaired saliva production. MicroCT of Akita ⁻/⁻ teeth revealed excessive enamel wearing and hypomineralization; immunostaining for Amel and Ambn was decreased. A striking feature was invasion of dentinal tubules with Streptococcus mitis and microabcesses that originated in the coronal pulp and progressed to pulp necrosis and periapical periodontitis. High levels of glucose also inhibited MD10-F2 cell proliferation and differentiation. Our findings provide the first evidence that hyperglycemia in combination with reduced saliva in a model of type1 DM leads to decreased enamel mineralization/matrix proteins and predisposes to excessive wearing and decay. Importantly, hyperglycemia adversely affects enamel matrix proteins and pulp repair. Early detection and treatment of hyperglycemia and hyposalivation may provide a useful strategy for preventing the dental complications of diabetes and promoting oral health in this population.

SGLT1 protein expression in plasma membrane of acinar cells correlates with the sympathetic outflow to salivary glands in diabetic and hypertensive rats

Salivary gland dysfunction is a feature in diabetes and hypertension. We hypothesized that sodium-glucose cotransporter 1 (SGLT1) participates in salivary dysfunctions through a sympathetic- and protein kinase A (PKA)-mediated pathway. In Wistar-Kyoto (WKY), diabetic WKY (WKY-D), spontaneously hypertensive (SHR), and diabetic SHR (SHR-D) rats, PKA/SGLT1 proteins were analyzed in parotid and submandibular glands, and the sympathetic nerve activity (SNA) to the glands was monitored. Basal SNA was threefold higher in SHR (P < 0.001 vs. WKY), and diabetes decreased this activity (∼50%, P < 0.05) in both WKY and SHR. The catalytic subunit of PKA and the plasma membrane SGLT1 content in acinar cells were regulated in parallel to the SNA. Electrical stimulation of the sympathetic branch to salivary glands increased (∼30%, P < 0.05) PKA and SGLT1 expression. Immunohistochemical analysis confirmed the observed regulations of SGLT1, revealing its location in basolateral membrane of acinar cells. Taken together, our results show highly coordinated regulation of sympathetic activity upon PKA activity and plasma membrane SGLT1 content in salivary glands. Furthermore, the present findings show that diabetic- and/or hypertensive-induced changes in the sympathetic activity correlate with changes in SGLT1 expression in basolateral membrane of acinar cells, which can participate in the salivary glands dysfunctions reported by patients with these pathologies.

Protein expression in salivary glands of rats with streptozotocin diabetes

Diabetes mellitus (DM) is a widespread disease with high morbidity and health care costs. An experimental animal model was employed, using morphological and biochemical methods, to investigate the effects of DM on the expression and compartmentation of salivary gland proteins. The distribution of proline-rich proteins (PRP), submandibular mucin (Muc10) and the regulatory (RI and RII) subunits of cyclic AMP-dependent protein kinase type I and type II was determined in the parotid and submandibular (SMG) glands of rats treated with streptozotocin. Quantitative immunocytochemistry of secretory granules in diabetic glands revealed decreases of 30% for PRP in both the parotid and SMG, and a 40% decrease in Muc10 in the SMG. Immunogold labelling showed that RII decreased in nuclei and the cytoplasm in diabetic acinar cells while labelling of secretory granules was similar in control and diabetic parotid. Electrophoresis and Western blotting of tissue extracts of two secretory proteins showed that the response to DM and insulin treatment was gland specific: PRP showed little change in the SMG, but decreased in the parotid in DM and was partially restored after insulin treatment. Photoaffinity labelling showed only RI present in the SMG and mainly RII in the parotid. The results of this and previous studies demonstrating highly specific changes in salivary protein expression indicate that the oral environment is significantly altered by DM, and that oral tissues and their function can be compromised. These findings may provide a basis for future studies to develop tests using saliva for diabetic status or progression in humans.

Volume-weighted mean volume of the submandibular gland acini in male and female diabetic rats

Mouth dryness is one of the complications of diabetes mellitus but there has been little work on morphological changes of the salivary glands. In the present study, the effects of diabetes mellitus on the serous and mucous acini of submandibular gland of male and female rats, 4 and 12 weeks after diabetes induction were studied. Male and female rats were divided into experimental and control subgroups. Diabetes was induced to experimental rats by streptozotocin. At the end of 4 and 12 weeks, the submandibular glands were removed, random sections obtained and volume-weighted mean acini volume was estimated by point-sampled intercepts method. The data revealed that volume reduction occurred only in serous acini in both male and female rats 12 weeks after diabetes induction and the others remained unchanged. The present research using stereological methods demonstrates that diabetes make some morphological changes in serous acini, the main exocrine part of the rat submandibular gland.

Changes in functioning of rat submandibular salivary gland under streptozotocin-induced diabetes are associated with alterations of Ca2+ signaling and Ca2+ transporting pumps

Xerostomia and pathological thirst are troublesome complications of diabetes mellitus associated with impaired functioning of salivary glands; however, their cellular mechanisms are not yet determined. Isolated acinar cells were loaded with Ca2+ indicators fura-2/AM for measuring cytosolic Ca2+ concentration ([Ca2+]i) or mag-fura-2/AM-inside the endoplasmic reticulum (ER). We found a dramatic decrease in pilocarpine-stimulated saliva flow, protein content and amylase activity in rats after 6 weeks of diabetes vs. healthy animals. This was accompanied with rise in resting [Ca2+]i and increased potency of acetylcholine (ACh) and carbachol (CCh) but not norepinephrine (NE) to induce [Ca2+]i transients in acinar cells from diabetic animals. However, [Ca2+]i transients mediated by Ca2+ release from ER stores (induced by application of either ACh, CCh, NE, or ionomycin in Ca2+-free extracellular medium) were decreased under diabetes. Application of inositol-1,4,5-trisphosphate led to smaller Ca2+ release from ER under the diabetes. Both plasmalemma and ER Ca2+-ATPases activity was reduced and the latter showed the increased affinity to ATP under the diabetes. We conclude that the diabetes caused impairment of salivary cells functions that, on the cellular level, associates with Ca2+ overload, increased Ca2+-mobilizing ability of muscarinic but not adrenergic receptors, decreased Ca2+-ATPases activity and ER Ca2+ content.

A central role for inflammation in the pathogenesis of diabetic retinopathy

Diabetic retinopathy is a leading cause of adult vision loss and blindness. Much of the retinal damage that characterizes the disease results from retinal vascular leakage and nonperfusion. Diabetic retinal vascular leakage, capillary nonperfusion, and endothelial cell damage are temporary and spatially associated with retinal leukocyte stasis in early experimental diabetes. Retinal leukostasis increases within days of developing diabetes and correlates with the increased expression of retinal intercellular adhesion molecule-1 (ICAM-1) and CD18. Mice deficient in the genes encoding for the leukocyte adhesion molecules CD18 and ICAM-1 were studied in two models of diabetic retinopathy with respect to the long-term development of retinal vascular lesions. CD18-/- and ICAM-1-/- mice demonstrate significantly fewer adherent leukocytes in the retinal vasculature at 11 and 15 months after induction of diabetes with STZ. This condition is associated with fewer damaged endothelial cells and lesser vascular leakage. Galactosemia of up to 24 months causes pericyte and endothelial cell loss and formation of acellular capillaries. These changes are significantly reduced in CD18- and ICAM-1-deficient mice. Basement membrane thickening of the retinal vessels is increased in long-term galactosemic animals independent of the genetic strain. Here we show that chronic, low-grade subclinical inflammation is responsible for many of the signature vascular lesions of diabetic retinopathy. These data highlight the central and causal role of adherent leukocytes in the pathogenesis of diabetic retinopathy. They also underscore the potential utility of anti-inflammatory treatment in diabetic retinopathy.

Salivary glands and noradrenergic transmission in diabetic rats

1 Type 2 diabetes is associated with diverse oral pathologies in which salivary flow reduction is one of the causes of these oral abnormalities. Scarce literature exists regarding noradrenergic transmission and adrenergic-induced salivary flow in submaxillary and parotid glands of type 2 diabetic rats. 2 We studied noradrenergic transmission as well as the secretory response to alpha1- and beta-adrenoceptor stimulation in the parotid and submaxillary glands of type 2 diabetic rats. 3 Diabetic rats exhibited diminished neuronal uptake, release and endogenous content of noradrenaline (NE) in both salivary glands. Further, NE synthesis was also diminished accompanied by decreased tyrosine hydroxylase activity. Salivary flow responses to alpha1-(methoxamine) and beta-(isoprenaline) adrenoceptor stimulation were reduced in the submaxillary as well as the parotid glands of diabetic rats. 4 Our results suggest that the reduction of noradrenergic transmission in the salivary glands of type 2 diabetic rats is in part responsible for the diminished salivary flow evoked by alpha1- and beta-adrenergic stimulation. Reduced noradrenergic activity may contribute to the pathophysiology of oral abnormalities in diabetic patients.

Lowered susceptibility of muscarinic receptor involved in salivary secretion of streptozotocin-induced diabetic rats

We investigated the responses of salivary secretion and the susceptibility of the muscarinic receptors in the salivary glands of the streptozotocin (STZ)-induced diabetic rats (STZ rats). Giving water ad libitum, the amount of whole saliva with no stimulation was similar in the STZ and the control rats. Pilocarpine increased salivary secretion in both groups, although the effect in the STZ rats was two to three fold less than in the control rats. If the animals were restricted from taking water for 6 h, salivary secretion was not slightly changed in the STZ rats in spite of a remarkable increase in the control. An obvious decrease in salivary secretion of the STZ rats was negatively correlated with an increase in urination. Furthermore, salivary secretion from the parotid gland was increased in a dose-dependent manner with pilocarpine in the control rats, but not in the STZ rats. In the [3H]quinuclidinyl benzilate (QNB) binding studies for muscarinic receptor of the STZ rats, Bmax was decreased in the parotid gland and Kd was increased in the submandibular gland. Competitive inhibition of [3H]QNB binding to both glands showed an increase in IC50 of pilocarpine and carbachol. These results suggest that a decrease in salivary secretion of STZ rats is not only induced by a water loss, but also closely associated with the lowered susceptibility of the muscarinic receptors.

Morphological effects of diabetes on the granular ducts and acini of the rat submandibular gland

Effects of experimental diabetes on rat submandibular glands have been documented, but earlier reports suggested that diabetes caused an extensive cellular degeneration and a replacement of the parenchymal cells by fibrous connective tissue. Such observations, however, are difficult to reconcile with the relatively normal physiological responsiveness of the gland (Anderson and Suleiman, 1989). This study, therefore, reexamined the histological, histochemical and ultrastructural effects of streptozotocin-induced diabetes on rat submandibular glands. The tissues were examined at 3 weeks, and 3 and 6 months after the induction of diabetes, and compared with glands from age-matched controls by both light and electron microscopy. Light microscopically, the proportional volumes of the acini and granular ducts remained constant in control rats at about 48% and 38% respectively. In diabetic animals the volume density of the acini increased progressively to 62%, whereas that of the granular ducts decreased to 20%. The diameter and number of granular ducts were reduced in diabetic animals, but acinar cell profile area was only affected 6 months after the induction of diabetes. Ultrastructurally, there was an accumulation of lipid in the acinar cells and, with increasing duration of diabetes, the number of autophagic structures in both the acini and the granular ducts increased. Although there was evidence of some cellular degeneration it was never excessive. Morphometry showed that the volume density of secretory granules within the acinar cells was unaffected, but there was a significant reduction in the volume density of secretory granules within the granular ducts. Thus, in the rat submandibular gland the greatest effect of streptozotocin-induced diabetes was to cause hypotrophic changes in the cells of the granular ducts. The relative contributions of a direct effect of insulin insufficiency and the hypogonadal effects of diabetes, however, are not known.

In vivo secretory responses of submandibular glands in streptozotocin-diabetic rats to sympathetic and parasympathetic nerve stimulation

Submandibular gland responses to sympathetic and parasympathetic nerve stimulation were studied in streptozotocin-diabetic rats. Morphologically, the acinar cells in control glands were relatively uniform in size and contained electron-lucent granules. The granular ducts were distinguished by the presence of electron-dense granules. With the exception of intracellular lipid droplets and the presence of a few autophagosomes in diabetic glands, no consistent differences in acinar cell structure were observed. In contrast, the diameter of the granular ducts and the granule content of their cells were less in diabetic glands. At 3 weeks sympathetic flow rate, salivary protein concentration, and total protein output were unaffected by diabetes. Sympathetic flow rate was greater at 3 months, and the concentration of protein in the saliva was lower. In 6-month diabetic rats flow rate remained increased, but protein concentration and total protein output were reduced. The decrease in salivary protein concentration at 3 and 6 months was accompanied by a reduction in secretory granule release from acinar and granular duct cells. No consistent differences in flow rate, protein concentration, protein output, or secretory granule release were observed following parasympathetic stimulation. We conclude that the effects of diabetes on nerve-stimulated flow rate and protein release depend on the duration of diabetes and the type of stimulation, and are independent of one another.

Lipid droplet accumulation and lipoprotein lipase activity in the rat salivary gland during the perinatal period

The submandibular and sublingual glands of foetal and newborn rats aged 21 days in utero to 7 days after birth were examined morphologically and biochemically. Lipid droplets tended to be localized in secretory cells, especially in their basal cytoplasm. The degree of droplet accumulation varied with the age of the rat. No droplets were observed before and immediately after birth. The number of accumulated droplets peaked 24-48 h after birth, then gradually decreased and reached normal levels by 5 days. In the salivary glands of fasted newborn rats, no lipid droplets were observed throughout the experiment. The amount of triacylglycerol reached its maximum level 1 day after birth; it then decreased gradually until 5 days and after that did not change. The amount of cholesterol did not change during postnatal development. Lipase activity attained its maximum level in the salivary glands immediately after birth and then decreased rapidly. It was higher in the glands of fasted than fed 1-day-old rats. Antiserum against lipoprotein lipase inhibited the salivary gland lipase activity in a dose-dependent manner, with 5 microliters of antiserum producing 60-70% inhibition. Non-immune serum had little effect. It was concluded that (1) accumulated lipid in the secretory cell cytoplasm of the salivary glands originates from ingested milk; (2) the principal component of accumulated lipid droplets is triacylglycerol; (3) 60-70% of the total lipase activity represents lipoprotein lipase; (4) an increase of lipoprotein lipase activity is recognizable before the accumulation of triacylglycerol.

Salivary glands in long-term alloxan-diabetic rats. A quantitative light and electron-microscopic study

Fifty untreated diabetic animals were compared with 58 age-matched non-diabetic controls. Reduced salivary gland weight was evident after one month's diabetes and this was unchanged after 12 months of diabetes. Submandibular/sublingual gland weight was proportional to the reduced body weight in the diabetic rats. Parotid gland weight, however, was proportionally more reduced. Only diabetic rats had lipid inclusions in the acinar cells of their submandibular glands and the morphometrically estimated amount of inclusions was positively correlated to the blood glucose level. Acinar cell size was significantly increased in long-term diabetic rats as compared with short-term diabetic rats and controls. Capillary basement membrane width was significantly increased in long-term diabetic rats compared with age-matched controls and with short-term diabetic rats. Thus, both the degree and duration of diabetes have a major effect on salivary gland morphology in alloxan diabetic rats.

Evolution of oxidative metabolism of submandibular gland and testes in pancreatectomized rats

The purpose of this work was to study the effects of prolonged mild diabetes on the submandibular salivary glands and testes of male rats over a 22-month period. Diabetes was induced by means of a subtotal pancreatectomy in a group of male rats. Body weight was registered monthly as well as the blood glucose values after fasting the animals. These values were compared with those obtained in sham-operated animals. The weight of pancreatectomized animals was always slightly higher than that of the controls although the differences were not significant, whereas blood glucose values were slightly higher in experimental animals. Testis O2 uptake in pancreatectomized animals was significantly lower than in controls 8 months after the operation. From this time on, the values of experimental animals rose, reaching a maximum value 20 months after the operation. Submandibular glands in pancreatectomized animals showed an O2 uptake that was always higher in experimental animals and reached a maximum value at 20 months.

Lipid accumulation in the major salivary glands of streptozotocin-diabetic rats

Four-five months after the induction of diabetes, salivary tissues of male Wistar rats were preserved by glutaraldehyde fixation or rapid freezing in dry-ice cooled hexane. Fixed tissues were either processed and embedded for light and electron microscopy, or frozen and, together with unfixed tissues, sectioned and stained with Oil Red 0 or by the calcium-lipase method. All diabetic glands had considerably more intracellular lipid than control ones. Lipid accumulation within parenchymal cells varied with the type of gland, and was more pronounced in animals with the highest serum-glucose levels. Serous cells of parotid and sublingual glands accumulated the greatest amount of lipid; lesser amounts were present in seromucous acinar cells of submandibular glands; little or none in mucous acinar cells of sublingual glands. There was no lipid in striated, granular or excretory ducts. Histochemical staining suggested that the intracellular lipid was mainly triglyceride which may accumulate by increased uptake for use as an energy source, or by decreased use in the synthesis of secretory granule and plasma-membrane material.

Levels of salivary lysozyme, lactoperoxidase, and lactoferrin in diabetic hamsters

In an attempt to clarify the mechanism(s) of increased susceptibility to oral infection in diabetics, we examined the levels of salivary antibacterial factors, including lysozyme, lactoperoxidase, and lactoferrin, in diabetic hamsters whose condition was induced with streptozotocin. Saliva was collected from these hamsters periodically for 19 weeks after the administration of streptozotocin. Diabetes persisted with significant hyperglycemia throughout the experiment after a single injection of streptozotocin. There was no significant difference between groups in the amount of saliva secreted. In diabetic hamsters, lysozyme activity decreased by 56% and lactoperoxidase activity decreased by 53% compared with the control hamsters 19 weeks after the administration of streptozotocin. There was no significant difference between groups in the amount of salivary lactoferrin. However, the ratio of lactoferrin to total protein increased to approximately double the amount of that of the control hamsters. Insulin treatment had a significant effect on lysozyme and lactoperoxidase activity, recovering 73 and 74% those of the controls, respectively, and the ratio of lactoferrin to total salivary protein reverted to normal values. Growth inhibition of Lactobacillus plantarum ATCC 8014 with whole saliva and amylase activity significantly decreased in diabetic hamsters. The position of each protein band of whole saliva on sodium dodecyl sulfate-polyacrylamide gel electrophoresis was almost the same for control and diabetic hamsters; however, there was some variability in band intensity.

Diabetes mellitus and associated oral manifestations: a review

Oral research concerning diabetes mellitus has revealed a number of clinical implications. These include, among others, the need for more intense management of the diabetic patient with periodontal disease because tissue destruction may be accelerated, the need for rapid control of oral infection in these patients in order to prevent exacerbation of the existing metabolic imbalance, and the desirability of performing a screening for diabetes mellitus on all patients exhibiting asymptomatic parotid enlargement. Despite the explosion of knowledge concerning diabetes mellitus that has occurred since the discovery of insulin, its definitive etiology continues to elude the scientific community and its treatment remains in the realm of clinical management rather than in that of prevention and cure. In the past, research on diabetes has focused on the role of insulin in seeking the fundamental etiology of diabetes and its complications. With the progression of research, it has become apparent that the initiation and progression of the disease probably involve the interplay of a multiplicity of factors. Hereditary and immunologic factors, as suggested earlier, appear to be operated on by environmental factors, subsequently altering the body's metabolic milieu with widespread primary and secondary effects. Fertile areas for future oral research in diabetes mellitus will include, therefore, genetics, immunology, enzymology, and basement membrane pathology. On the cellular and molecular levels, particularly, the oral cavity and associated structures comprise a somewhat under-investigated area in diabetes mellitus research and, thus, hold great promise for increasing our knowledge of this complex disease.

A morphologic study of the recovery of the rat submandibular gland after retrograde infusion. I. Water-soluble radiographic contrast medium

The recovery of the rat submandibular gland after retrograde infusion of water-soluble radiographic contrast medium was studied using an experimental model. During continuous monitoring of the developing intraglandular pressure, the glands were subjected to ductal and slight parenchymal filling or heavy parenchymal filling with the medium. The animals were killed after varying recovery periods, and the tissue was prepared for light and electron microscopic examination. Dilation of the ductal lumina, induced during ductal and slight parenchymal filling, was successively reduced and, generally, the parenchyma had a normal appearance at 30 h. In glands subjected to heavy parenchymal filling, the changes in the intralobular ducts were more pronounced and were also seen at later times after infusion. Alterations in the acini, comprising fusion of secretory granules, vacuole formation and dilation of the acinar lumina and intercellular canaliculi, were observed. At later times, atrophy of the parenchymal cells occurred together with an apparent proliferation of the connective-tissue stroma, as well as an increase in the number of small blood vessels. An inflammatory cell-infiltrate was seen in both groups of animals, but was most prominent in glands subjected to heavy parenchymal filling. The infiltrate, comprised primarily of macrophages and polymorphonuclear leukocytes, reached a peak at 20 h after infusion. At later times, mast cells and occasional eosinophils were seen. The observed alterations and the pattern of recovery are most likely due to the induced intraglandular pressure and the following inflammatory reaction. It is also possible that the changes, to some extent, are influenced by the presence of the contrast medium in the tissue.

Effects of irradiation on the submandibular gland of the rat. An enzyme histochemical and ultrastructural study

Single-dose cervical irradiation by cobalt 60 in rats induced lasting functional disturbances of the submandibular gland which were excessive when compared with the relative integrity of the gland as seen under the light microscope. Enzyme histochemical and ultrastructural studies revealed severe damage shortly after exposure with appearance of karyolytic bodies and autophagosomes accompanied by increased hydrolase activity. Mitochondrial alterations were concomitant with diminished ductal oxidative enzyme activity. Although most of these alterations resolved rapidly as a result of acinar and ductal cell repair and regeneration originating in the intercalated ducts, secretory abnormalities were still observed two months after exposure as evidenced by the accumulation of granules in acinar cells and the heterogeneity of ductal cell granules. These anomalies, comparable to those observed in sialadenoses, probably result from persistent alterations of intralobular nerve endings.