Drosophila salivary gland proteins and pupation

Pulse-labeling experiments of salivary glands from the prepupal stages of development showed selectively high rates of synthesis of a set of low molecular weight proteins (6K–12K). These proteins are stably maintained in the salivary glands during prepupal development and are subsequently transported to the pupation fluid (found between the pupal case and the prepupal cuticle) when pupation occurs. These small polypeptides are very basic with the major components having isoelectric points of 8.6–8.7 and the minor components having isoelectric points of 9.1–9.5. This study shows the continuing function of the salivary glands—specifically, the synthesis and secretion of a set of proteins with a putative role in pupation.     

Calcium signaling defects underlying salivary gland dysfunction

Salivary glands secrete saliva, a mixture of proteins and fluids, which plays an extremely important role in the maintenance of oral health. Loss of salivary secretion causes a dry mouth condition, xerostomia, which has numerous deleterious consequences including opportunistic infections within the oral cavity, difficulties in eating and swallowing food, and problems with speech. Saliva secretion is regulated by stimulation of specific signaling mechanisms within the acinar cells of the gland. Neurotransmitter-stimulated increase in cytosolic [Ca²⁺] ([Ca²⁺]_i) in acinar cells is the primary trigger for salivary fluid secretion from salivary glands, the loss of which is a critical factor underlying dry mouth conditions in patients. The increase in [Ca²⁺]_i regulates multiple ion channel and transport activities that together generate the osmotic gradient which drives fluid secretion across the apical membrane. Ca²⁺ entry mediated by the Store-Operated Ca²⁺ Entry (SOCE) mechanism provides the essential [Ca²⁺]_i signals to trigger salivary gland fluid secretion. Under physiological conditions depletion of ER-Ca²⁺ stores is caused by activation of IP3R by IP3 and this provides the stimulus for SOCE. Core components of SOCE in salivary gland acinar cells are the plasma membrane Ca²⁺ channels, Orai1 and TRPC1, and STIM1, a Ca²⁺-sensor protein in the ER, which regulates both channels. In addition, STIM2 likely enhances the sensitivity of cells to ER-Ca²⁺ depletion thereby tuning the cellular response to agonist stimulation. Two major, clinically relevant, conditions which cause irreversible salivary gland dysfunction are radiation treatment for head-and-neck cancers and the autoimmune exocrinopathy, Sjögren's syndrome (pSS). However, the exact mechanism(s) that causes the loss of fluid secretion, in either condition, is not clearly understood. A number of recent studies have identified that defects in critical Ca²⁺ signaling mechanisms underlie salivary gland dysfunction caused by radiation treatment or Sjögren's syndrome (pSS). This chapter will discuss these very interesting and important studies.     

Dendritic cell tumor in a salivary gland lymph node: a rare differential diagnosis of salivary gland neoplasms

Background

We investigated the occurrence and clinical significance of mucin expression in ampullary adenocarcinoma.

Methods

We retrospectively analyzed clinical, pathological, and survival data from 74 ampullary adenocarcinoma patients who received radical operation from January 2004 to November 2006.

Results

The tumors were located in the lower end of the common bile duct (46%), papillary duodenum (42%), and ampullary duodenum (12%), and expressed MUC1 (72%), MUC2 (20%), MUC5AC (43%), and MUC6 (27%). Expression of MUC1 was associated with tumor differentiation (OR: 4.71, 95% CI: 1.26, 17.66, P = 0.021). Expression of MUC5AC was associated with age (OR: 1.07, 95% CI: 1.11, 1.14, P = 0.026) and less vessel invasion(OR: 0.14, 95% CI: 0.03, 0.72, P = 0.019). The survival rates were not significantly different when patients had or had no expression of MUC1, MUC2, MUC5AC, or MUC6 in tumor. Patients with tumors positive for MUC5AC in the papillary duodenum had worse survival than those with tumors negative for MUC5AC (P = 0.044).

Conclusions

Expression of MUC1 was high (72%) in ampullary adenocarcinoma, while expressions of MUC2, MUC5AC, and MUC6 were lower. Mucins are useful markers to diagnose and identify ampullary adenocarcinoma, particularly in determining the degree of malignancy of ampullary adenocarcinoma.     

Electron microscope studies on salivary gland cells

Summary A study of the ultrastructure of the nuclear envelope of the salivary glands cells in the sciarid Bradysia suggests that it probably consists of four membranes, instead of two as found in most cells. The fine structure associated with the pores closely resembles that described in amphibian oocytes by Wischnitzer 1958.British Empire Cancer Campaign.     

The salivary gland chromosomes of Anopheles hectoris

The salivary gland chromosome map of Anopheles hectoris is described and figured. It is proposed that this map be considered the standard for this species. The hectoris chromosomes show a close relationship to those of Anopheles pseudopunctipennis pseudopunctipennis.     

High-level salivary gland expression in transgenic mice

A 7.1 kb mini-gene construct containing cloned DNA from the murine parotid secretory protein (PSP) gene with 6.2 kb of the promoter, has previously been shown to direct specific mRNA expression to the salivary glands in transgenic mice. However, the level of transgene expression in the parotid gland was only a few percent of the endogenous level. This indicated that elements necessary for high-level expression are still to be found. In this study, we have searched for such regulatory elements in additional flanking regions by using a 25 kb clonedPsp ^b fragment containing the complete structural gene, 11.4 kb of 5-flanking sequence, and 2.5 kb 3-flanking sequence as a transgene. To distinguish the expression of the transgene from that of the endogenous gene, we took advantage of an allelic difference, using an oligonucleotide that recognized the mRNA fromPsp ^b and the transgene but not that from the other allele,Psp ^a . The expression of the transgene was examined in animals homozygous forPsp ^a . Three independent integrations all exhibited a level of parotid-gland-specific expression that corresponded to that of the endogenous gene. Thus, sequences responsible for this high-level PSP mRNA expression are situated within the genomic DNA of the transgene.