Biomedical subjects

P C Denny

Publications and source records attributed to P C Denny.

At least 19 recordsLinked to original sources

PubMed2004

The gene encoding mouse Muc19: cDNA, genomic organization and relationship to Smgc.

We previously demonstrated expression of full-length transcripts for sublingual mucin apoprotein, Muc19, of approximately 24 kb (Fallon MA, Latchney LR, Hand AR, Johar A, Denny PA, Georgel PT, Denny PC, and Culp DJ. Physiol Genomics 14: 95-106, 2003). We now describe the complete sequence and genomic organization of the apomucin encoded by 43 exons. Southern analyses indicate a central exon of approximately 18 kb containing 36 tandem repeats, each encoding 163 residues rich in serine and threonine. Full-length transcripts are an estimated 22,795 bp in length that span 106 kb of genomic DNA. The transcriptional start site is 24 bp downstream of a TATA box and 42 bp upstream of the conceptual translational start codon. The putative apoprotein has an estimated mass of 693.4 kDa and contains 7,524 amino acids (80% serine, threonine, glycine, alanine, and proline). We present a model for rat Muc19 transcripts and compare the conceptually translated Muc19 proteins for mouse, rat, pig, and the 3' end of human Muc19. Conserved among these apoproteins are a signal peptide, a large tandem repeat region, von Willebrand factor type C and D domains, a trypsin inhibitor-like Cys-rich domain, and a COOH-terminal cystine knot-like domain. Southern blot analyses indicate transcripts for Muc19 and Smgc (submandibular gland protein C) are splice variants of a larger gene, Muc19/Smgc. Comparative Northern analyses between the major salivary glands demonstrate highly selective Muc19 expression in neonatal and adult sublingual glands, whereas Smgc is expressed in neonatal submandibular and sublingual glands. Regulation of Muc19/Smgc gene expression is discussed with respect to alternative splicing and mucous cell cytodifferentiation.

Amino Acid Sequence↗

PubMed2003

The sld mutation is specific for sublingual salivary mucous cells and disrupts apomucin gene expression.

NFS/N-sld mice harbor a spontaneous autosomal recessive mutation, sld (sublingual gland differentiation arrest) and histologically display attenuated mucous cell expression in sublingual glands (Hayashi et al. Am J Pathol 132: 187-191, 1988). Because altered serous demilune cell expression is unknown, we determined the phenotypic expression of this cell type in mutants. Moreover, we evaluated whether absence of glycoconjugate staining in 3-day-old mutant glands is related to disruption in apomucin gene expression and/or to posttranslational glycosylation events. Serous cell differentiation is unaffected, determined morphologically and by serous cell marker expression (PSP, parotid secretory protein; and Dcpp, demilune cell and parotid protein). Conversely, apical granules in "atypical" exocrine cells of mutant glands are PSP and mucin negative, but contain abundant SMGD (mucous granule marker). Age-related appearance of mucous cells is associated with expression of apomucin gene products, whereas SMGD expression is unaltered. "Atypical" cells thus appear specified to a mucous cell fate but do not synthesize mucin glycoproteins unless selectively induced postnatally, indicating the sld mutation disrupts apomucin transcriptional regulation and/or decreases apomucin mRNA stability.

Animals↗

PubMed2000

Salivary mucin as related to oral Streptococcus mutans in elderly people.

MG1 (MUC5b and MUC4) and MG2 (MUC7), predominant mucins in human whole saliva, provide lubrication and antimicrobial protection for oral tissues. This study examines potential relationships between Streptococcus mutans titers in the oral cavity and the following: mucin concentrations; unstimulated and stimulated whole saliva flow rates; decayed, missing, and filled tooth surfaces; and age of 24 elderly patients. S. mutans titers were determined using Denticult SM. Mucin concentrations were determined using Stains-all, sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Logistic regression was used to identify potential relationships between the above variables. S. mutans classification served as the dependent variable. The remaining variables were possible predictor variables. The best model for predicting S. mutans category contained log MG2 as a predictor variable for all of its parameter estimates. No other set of parameter estimates were statistically significant. These results suggest that elevated S. mutans titers are significantly associated with diminished concentrations of MG2 in unstimulated whole saliva, as quantified in mucin-dye binding units.

Aged↗

PubMed1999

Evidence of a phenotypically determined ductal cell lineage in mouse salivary glands.

The submandibular salivary gland of mice contains a parenchymal element, the granular duct, which matures peripubertally from the striated ducts. Granular duct cells also differentiate from intercalated ducts in the adult mouse submandibular gland. Using preproNGF-A as a signature protein of mature granular duct cells, this study inquired if phenotypic determination might have occurred earlier than the first signs of cellular differentiation. Results from RT-PCR indicate the presence of preproNGF-A transcripts at all postnatal stages of development of the submandibular glands, as well as in adult sublingual glands. The preproNGF-A transcript was also detected prenatally as early as embryonic day 17 in the submandibular/sublingual complex. Using an antibody directed specifically against the "pre" peptide, immunocytochemistry showed preproNGF-A localized in the granular ducts and striated ducts of the adult submandibular gland. In addition preproNGF-A was detected throughout the first order branches of the intercalated duct system. In the neonatal gland, preproNGF-A was found in the large tubules that differentiate to the striated ducts. The early appearance of preproNGF-A in the histological lineage that sequentially gives rise to striated ducts and then to granular ducts suggests that this lineage is phenotypically determined as early as birth. An undifferentiated stage of the phenotypically determined lineage also appears to be retained in the intercalated duct system to provide progenitors for subsequent differentiation in the adult gland. Throughout development of the sublingual gland, preproNGF-A was detectable in the striated ducts or in their predecessors, suggesting that they may also represent a phenotypically determined cell lineage similar to that of the submandibular gland.

Amino Acid Sequence↗

PubMed1999

Dynamics of parenchymal cell division, differentiation, and apoptosis in the young adult female mouse submandibular gland.

The submandibular salivary gland of the young adult female mouse has two secretory cell types, acinar and granular duct, which are separated by intercalated ducts. Based on the occurrence of autologous cell division in these cells, they have been traditionally classified as expanding populations. However, differentiation from stem or progenitor cells in the intercalated ducts, usually associated with renewing populations, has also been detected. The question of renewing or expanding populations is resolved by quantitating and integrating the rates of autologous cell division, differentiation, and apoptosis for each cell type. The integrated data shows that both acinar and granular duct cell populations exhibit a substantial positive growth index, whereas the growth index for the intercalated duct cells is moderately negative. On balance, it suggests that the submandibular gland of the young adult female mouse is still growing. Comparison of young female mice with older females suggests that, although overall parenchymal growth slows with age, there is no longer a net loss of intercalated duct cells. Comparison with young adult male submandibular glands indicates that gender differences exist in the rates and mechanisms used for maintaining the different cell populations. The acinar and granular duct cell populations in young adult female mouse submandibular glands are expanding at the expense of the intercalated duct cell population, which appears to be contracting.

Age Factors↗

PubMed1999

High levels of GM(1)-ganglioside and GM(1)-ganglioside beta-galactosidase in the parotid gland: a new model for secretory mechanisms of the parotid gland.

A new model for the subcellular basis of parotid secretion is presented in this article. GM(1)-ganglioside, typically found in neural tissues, is shown to be abundant in the parotid gland. This ganglioside may play a central role in membrane turnover mechanisms underlying exocytosis/endocytosis in its role as a promoter of membrane fusion or a fusogen. The lysosome and lysosomal hydrolases also play a central role in this model in catabolism of GM(1)-ganglioside. Consequently, high levels of the lysosomal hydrolase acidic beta-galactosidase are demonstrated in the salivary gland. GM(1)-gangliosidosis of the parotid glands, as described in mice, appears to be the first single-gene heritable disease found so far in the salivary glands.

Adenoma, Pleomorphic↗

PubMed1998

Mouse submandibular gland mucin: embryo-specific mRNA and protein species.

Mouse submandibular salivary gland (SMG) mucin is the primary histodifferentiation product of submandibular epithelia. We demonstrate marked differences between embryonic, neonatal, and adult SMG mucin mRNA and protein by Northern and Western blot analyses: E17 and 1-day-old neonates exhibit two unique mucin transcripts (1.20 and 0.85 kb) which are approximately 19% greater or smaller in size than the single (1.01 kb) adult transcript. Two embryonic protein isoforms (Mr approximately 110 and 152 kDa) are immunodetected compared to a single adult protein (Mr approximately 136 kDa), with the larger (approximately 152 kDa) embryonic isoform persisting in neonatal glands. Mucin transcripts are localized to the branching epithelia in E14 and older SMGs, with increased hybridization signal being seen in terminal bud and proacinar epithelial cells with age; a significant 26% increase in transcript levels is detected by RNase protection assay between E14 and E19. By contrast, submandibular mucin protein is not immunodetected until E17, being primarily immunolocalized to terminal bud and proacinar epithelial cell membranes. Our data clearly shows that substantial qualitative differences exist between embryonic and adult SMG mucin mRNA and protein.

Animals↗

PubMed1997

Salivary glands: a paradigm for diversity of gland development.

The major salivary glands of mammals are represented by three pairs of organs that cooperate functionally to produce saliva for the oral cavity. While each type of gland produces a signature secretion that complements the secretions from the other glands, there is also redundancy as evidenced by secretion of functionally similar and, in some cases, identical products in the three glands. This, along with their common late initiation of development, in fetal terms, their similarities in developmental pattern, and their proximate sites of origin, suggests that a common regulatory cascade may have been shared until shortly before the onset of overt gland development. Furthermore, occasional ectopic differentiation of individual mature secretory cells in the "wrong" gland suggests that control mechanisms responsible for the distinctive cellular composition of each gland also share many common steps, with only minor differences providing the impetus for diversification. To begin to address this area, we examine here the origins of the salivary glands by reviewing the expression patterns of several genes with known morphogenetic potential that may be involved based on developmental timing and location. The possibility that factors leading to determination of the sites of mammalian salivary gland development might be homologous to the regulatory cascade leading to salivary gland formation in Drosophila is also evaluated. In a subsequent section, cellular phenotypes of neonatal and adult glands are compared and evaluated for insights into the mechanisms and lineages leading to cellular diversification. Finally, the phenomena of proliferation, repair, and regeneration in adult salivary glands are reviewed, with emphasis on the extent to which the cellular diversity is reversible and which cell type other than stem cells has the ability to redifferentiate into other cell types.

Animals↗

PubMed1996

Mouse submandibular gland salivary apomucin contains repeated N-glycosylation sites.

A cDNA clone encoding mouse submandibular gland salivary mucin apoprotein was isolated and characterized. The mucin cDNA encodes a protein of 273 amino acids with a calculated molecular weight of 29,606. This apomucin is approximately 60% Thr, Ser, and Pro, and has a pI of 11.25. In addition to the signal sequence, the apomucin can be divided into four structural domains. The first of these contains over 30% Thr, Ser, and Pro, but only a few probable O-glycosylation sites. The second domain contains 10 repeats, each 9 or 13 amino acids in length, with Thr representing more than 50% of the amino acids, while Ser accounts for only 2%. Each repeat begins with a putative N-glycosylation site; hence this domain likely contains both N- and O-linked oligosaccharides. The third domain lacks a repeat motif, but is rich in both Thr and Ser, and therefore is potentially highly O-glycosylated. The final domain is composed mainly of basic and non-polar amino acids and does not contain Cys. This mucin shows considerable homology with the rat submandibular salivary mucin, but little overall homology with other mucins. In situ hybridization verifies that the mucin transcript is localized primarily in the acinar cells of the submandibular gland.

Amino Acid Sequence↗

PubMed1995

Characterization of asparagine-linked oligosaccharides on a mouse submandibular mucin.

The asparagine-linked oligosaccharides from an adult female mouse submandibular gland mucin were released by treatment with peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase F or endo-beta-N-acetylglucosaminidase H. Endo-beta-N-acetylglucosaminidase H appeared to be more effective at releasing the asparagine-linked oligosaccharides from this mucin than was peptide-N4-(N-acetyl-beta-glucosaminyl)-asparagine amidase F. After quantitative reductive labelling with the fluorophore, 8-aminonaphthalene-1,3,6-sulphonic acid, the oligosaccharides were separated by polyacrylamide gel electrophoresis and isolated. The individual oligosaccharides were sequenced by a battery of recombinant exoglycosidases. Approximately 50% of the oligosaccharides were of the high-mannose type. The five-mannose member of this family was the most prevalent. The second group of oligosaccharides were of the non-bisected hybrid type. No complex asparagine-linked oligosaccharides were detected. The hybrids exhibited both biantennary and triantennary branching patterns. The triantennary hybrid was the most common hybrid at > 30% of all oligosaccharides. With approximately 98% of the hybrid oligosaccharides sialylated and all lacking a bisecting N-acetylglucosamine, these oligosaccharides as a group have been only rarely observed in other glycoproteins. The fully sialylated triantennary hybrid may be unique.

Animals↗

PubMed1994

cDNA cloning, sequencing and in situ localization of a transcript specific to both sublingual demilune cells and parotid intercalated duct cells in mouse salivary glands.

A cDNA clone derived from mouse sublingual gland was isolated from lambda-phage cDNA library. Northern blot hybridization indicated that the transcript from which it was derived was approx. 700 nucleotides in length. This mRNA encoded a protein of about 20 kDa, as determined by hybrid selection and cell-free translation. Conceptual translation of the cDNA clones showed that p20 is 170 amino acids in length. The putative protein is hydrophobic in nature, is neither a mucin-like protein nor does its amino acid sequence or composition resemble the other known mouse proteins. However, the amino acid sequence of p20 suggests that it may be from a gene or gene family homologous to rat common salivary protein 1. The p20 mRNA also appears to share a non-random degree of sequence homology with the cysteine-rich domains of bovine and porcine submandibular mucins. The p20 mRNA is abundant in the mouse sublingual gland, and its expression is approx. nine times greater than in the parotid gland. In situ hybridizations localized the p20 mRNA exclusively in the demilune cells of the sublingual gland and in the intercalated duct cells of the parotid gland. It is detectable in the neonatal and adult submandibular gland at very low levels, but is absent from liver, heart, brain, thymus, spleen, lens and lacrimal glands.

Amino Acid Sequence↗

PubMed1993

Proliferative and structural differences between male and female mouse submandibular glands.

Sexual dimorphism has been observed in salivary glands of many species. In this study, evidence for sexual differences in adult mouse submandibular gland is extended beyond parenchymal cell composition, size, and volumes to include patterns of DNA synthesis and complexity of ductal branching. Computer-assisted three-dimensional reconstructions also revealed differences in overall organization of secretory complexes. Consistent with observations by others, granular intercalated duct cells were absent, while striated granular duct cells were low in proportion in the male glands relative to female glands. When the mean of average cell volumes were compared, acinar (AC) cells were smaller than granular duct (GD) cells in the male, but in the female the reverse was true. Furthermore, in addition to differences in average volumes of GD cells, the average volume of AC cells was significantly greater in females than males. The most dramatic evidence for sexual dimorphism was observed following a 90-min labeling with 3H-thymidine. Though all cell types showed DNA replication activity, the intercalated duct (ID) cells were substantially more active than AC and GD cells in the female, while in the male the GD cells, ID cells, and AC cells all showed approximately equal activity. Three-dimensional reconstructions indicated that the female possessed a more highly branched intercalated duct system and that the GD usually terminated within a secretory complex, whereas in males the GD typically passes through a secretory complex and forms a prominent cap-like structure on the opposite side.

Animals↗

PubMed1993

Parenchymal cell proliferation and mechanisms for maintenance of granular duct and acinar cell populations in adult male mouse submandibular gland.

To evaluate proliferation as a factor in maintenance of parenchymal cell populations in adult male mouse submandibular glands, a variety of surveys were conducted following a pulse with 3H-thymidine. Striated granular duct (SGD) cells had the highest labeling index, followed by intercalated duct (ID) cells, then acinar (AC) cells, and granular duct (GD) cells had the lowest. These cell types showed from 30% to 60% completion of mitosis by 24 hr, with SGD, AC, and GD showing a likely second wave of mitosis sometime between 2 and 7 days after the pulse. About 40% of the pulse-labeled cells still remained as single cells at 42 days after the pulse. Repeat divisions in daughter cells of the primary labeled cells were very rare. A shift in the pattern of labeled cells at the ID-GD junction indicates that ID and SGD cells in this compartment are differentiating to GD cells. Further comparison of the magnitude of this conversion with the amount of noncompartmental GD cell proliferation provided a basis for calculating that approximately 70% of GD cell population maintenance occurs by self-proliferation, and the remaining 30% is contributed by differentiation from ID and SGD cells. A similar survey at the ID-acinus junction showed no evidence of conversion of ID cells to AC cells indicating that most, if not all, proliferative activity leading to AC cell population maintenance occurs by self-proliferation. Finally, based in part on structural changes at the ID-GD junction during the survey period, a pattern of cell conversion described as "in situ differentiation" is proposed. When this pattern is carried to fruition, this explains several structural features of the secretory complex typical to the male pattern submandibular gland. The proposed mechanism is supported by a three-dimensionally reconstructed sequence of likely intermediate structures.

Animals↗

PubMed1993

DNA synthesis and development strategies with possible consequences on sexual dimorphism in adult mouse submandibular glands.

This article summarizes a series of recent studies that broaden the criteria for sexual dimorphism in adult mouse submandibular gland. From these observations, a hypothesis is presented, suggesting that the gross histological differences that are characteristic of adult sexual dimorphism in the gland secondarily result from differences in the activities of three fundamental cellular processes, that is, rates of cell proliferation, cell sizes, and ongoing patterns of differentiation.

Animals↗

PubMed1992

Increased mucin levels in submandibular saliva from mice following repeated isoproterenol treatment.

Mucin decreases with age in the submandibular glands of mice and can be restored by chronic administration of isoproterenol. Mice were given repeated injections of isoproterenol to determine if the increase of mucin in the submandibular gland leads to elevated levels of mucin in the submandibular saliva. Mucin was significantly elevated in both the gland and the saliva after isoproterenol. Gland contents of mucin and the concentration of mucin in their salivas were positively correlated for both the isoproterenol (p = 0.01) and the control group (p less than 0.01).

Animals↗

PubMed1992

Comparison of whole saliva flow rates and mucin concentrations in healthy Caucasian young and aged adults.

Unstimulated and chewing-stimulated whole saliva samples were obtained from 42 healthy Caucasians; 21 were between 18 and 35 years of age, and 21 between 65 and 83 years of age. The unstimulated salivary flow rate was significantly lower in the aged group, but the stimulated flow rate was significantly higher in the aged than in the young group. Both groups showed significantly increased flow during salivary stimulation. MG1 and MG2 concentrations in unstimulated and stimulated saliva samples were significantly lower in the aged group. There were no significant correlations between salivary flow rates and MG1 and MG2 concentrations.

Adolescent↗

PubMed1991

The effect of ageing on mucin contents in mouse submandibular glands.

There may be deleterious effects if there is an age-dependent reduction in mucin composition or content in salivary glands. To assess whether there was an effect of age in submandibular glands from male mice aged 3 months, 10 and 20 months and 27, 29 and 30 months, mucin, protein and sialic acid were quantitated. Changes in wet weight per gland and protein per gland were highly significant (p less than 0.001), as tested by analysis of variance, and the means for both were highest in middle aged glands. While sialic acid per gland showed no significant change from middle aged to old glands, mucin per gland showed an age-related decrease (p less than 0.01) when comparing either young or middle aged glands with old glands.

Aging↗

PubMed1991

Increased mucin levels in submandibular glands of aged male mice after chronic isoproterenol treatment.

Mucin levels are reduced in submandibular glands of mice during ageing. Isoproterenol (IPR) was given to mice 27 and 29 months old to assess whether levels of mucin could be restored to levels similar to those in younger mice. When compared with controls, mucin levels per gland were significantly elevated (p less than 0.05) after IPR treatment, and exceeded the peak amounts in young animals. Mucin concentrations were also higher after IPR. These observations support the contention that the gland has the ability to return to or exceed pre-senescent levels of mucin. Mean sialic acid levels were elevated in each experiment after IPR treatment. There was evidence for significant diurnal variation in mucin in the aged control animals, but little evidence for such a relationship in the IPR-treated animals. After administration of pilocarpine there was a modest stimulation of sialic acid and protein levels in 20-month-old animals while mucin levels showed virtually no indication of stimulation.

Aging↗