Biomedical subjects

S D Tran

Publications and source records attributed to S D Tran.

10 recordsLinked to original sources

PubMed2002

Absence of tight junction formation in an allogeneic graft cell line used for developing an engineered artificial salivary gland.

An essential structural feature of fluid-secreting epithelial tissues is the presence of tight junctions. To develop a tissue-engineered organ capable of fluid secretion, the cellular component must establish these structures. As part of efforts to create an engineered artificial salivary gland, we have examined the ability of a candidate allogeneic graft cell line, HSG, to produce several key tight junction proteins, as well as to exhibit functional activities consistent with effective tight junction strand formation. In contrast to results obtained with a control kidney cell line, MDCK-II, HSG cells were unable to synthesize four important tight junction-associated proteins: ZO-1, occludin, claudin-1, and claudin-2. In addition, unlike MDCK-II cells, HSG cell monolayers could not restrict paracellular permeability. HSG cells were, thus, unable to generate significant transepithelial electrical resistance or serve as an effective barrier to osmotically imposed fluid movement. Furthermore, these two functional activities could not be reconstituted via the stable transfection of HSG cells with cDNAs encoding either claudin-1 or claudin-2. We conclude that because of their inability to form tight junctions, HSG cells are unsuitable for use as an allogeneic graft cell in an artificial salivary fluid secretory device. These studies also emphasize the importance of graft cell selection in artificial organ development, as certain required characteristics may be difficult to reengineer.

Cell Line↗

PubMed2001

Persistent presence of Bacteroides forsythus as a risk factor for attachment loss in a population with low prevalence and severity of adult periodontitis.

BACKGROUND: Previous longitudinal studies investigating the role of microorganisms in periodontitis have focused on subjects with a high prevalence and severity of disease. The complex profile of microbial species in severe cases of periodontitis might not allow us to differentiate which bacterial species initiate disease or which species simply proliferate after disease progression. This prospective longitudinal study followed a group of 205 subjects who showed a low prevalence and severity of adult periodontitis, and thus allowed us to monitor early microbiological changes in the development of periodontitis. METHODS: Subgingival plaque was collected from proximal surfaces of a posterior sextant at 6-month intervals for 2 years. During the monitoring period, 44 subjects had either attachment loss or attachment gain. Using multiplex polymerase chain reaction (PCR), all plaque samples from those 44 subjects were analyzed for the presence of Actinobacillus actinomycetemcomitans, Bacteroides forsythus, and Porphyromonas gingivalis. RESULTS: Both subjects with attachment loss and those with attachment gain had a high prevalence of these 3 periodontal pathogens. The mere presence of any of the 3 species at a site could not predict future attachment loss at that specific site. However, subjects with a persistent presence of B. forsythus at any site across all visits had 5.3 times higher odds of having at least one site in their mouth losing attachment compared to subjects with occasional or no presence of B. forsythus. CONCLUSIONS: The persistence of B. forsythus identified subjects at higher risk, but not which specific sites in those subjects would lose attachment.

Actinobacillus Infections↗

PubMed2000

Diagnosis of vertebral metastasis, epidural metastasis, and malignant spinal cord compression: are T(1)-weighted sagittal images sufficient?

The objective of this study was to determine whether T(1)-weighted sagittal images alone are adequate in the diagnosis of vertebral metastasis, epidural metastasis, and malignant spinal cord compression. Ninety-four complete magnetic resonance (MR) studies of the spinal column (a complete study consisting of T(1)-weighted sagittal images, T(2)-weighted sagittal images, and T(1)- and/or T(2)-weighted axial images) and 94 T(1)-weighted sagittal images alone (a subset of the complete studies) from 57 consecutive cancer patients over the last 2 years with clinically suspected cord compression were blindly and independently evaluated by four radiologists. The complete MR studies were used as the standard. Overall, the sensitivity of T(1)-weighted sagittal images alone to vertebral metastasis (87%) was statistically greater than cord compression (70%) (p = 0.05), and statistically greater than epidural metastasis (46%) (p </= 0.02). The specificity for cord compression (97%) was greater than the specificity for epidural metastasis (89%) (p = 0.03), and greater than the specificity for vertebral metastasis (83%) (p </= 0.02). There was a strong trend for better detection of cord compression overall and better detection of vertebral metastasis in the cervical spine by the most experienced radiologist. Complete studies of the spine are necessary in the diagnosis of vertebral metastasis, epidural metastasis, and cord compression, particularly with less experienced radiologists.

Adult↗

PubMed1999

Improved multiplex PCR using conserved and species-specific 16S rRNA gene primers for simultaneous detection of Actinobacillus actinomycetemcomitans, Bacteroides forsythus, and Porphyromonas gingivalis.

Among putative periodontal pathogens, Actinobacillus actinomycetemcomitans, Bacteroides forsythus, and Porphyromonas gingivalis are most convincingly implicated as etiological agents in periodontitis. Therefore, techniques for detection of those three species would be of value. We previously published a description of a multiplex PCR that detects A. actinomycetemcomitans and P. gingivalis. The present paper presents an improvement on that technique, which now allows more sensitive detection of all three periodontal pathogens. Sensitivity was determined by testing serial dilutions of A. actinomycetemcomitans, B. forsythus, and P. gingivalis cells. Primer specificity was tested against (i) all gene sequences from the GenBank-EMBL database, (ii) six A. actinomycetemcomitans, one B. forsythus, and four P. gingivalis strains, (iii) eight different species of oral bacteria, and (iv) supra- and subgingival plaque samples from 20 healthy subjects and subgingival plaque samples from 10 patients with periodontitis. The multiplex PCR had a detection limit of 10 A. actinomycetemcomitans, 10 P. gingivalis, and 100 B. forsythus cells. Specificity was confirmed by the fact that (i) none of our forward primers were homologous to the 16S rRNA genes of other oral species, (ii) amplicons of predicted size were detected for all A. actinomycetemcomitans, B. forsythus, and P. gingivalis strains tested, and (iii) no amplicons were detected for the eight other bacterial species. A. actinomycetemcomitans, B. forsythus, and P. gingivalis were detected in 6 of 20, 1 of 20, and 11 of 20 of supragingival plaque samples, respectively, and 4 of 20, 7 of 20, and 13 of 20 of subgingival plaque samples, respectively, from periodontally healthy subjects. Among patients with periodontitis, the organisms were detected in 7 of 10, 10 of 10, and 7 of 10 samples, respectively. The simultaneous detection of three periodontal pathogens is an advantage of this technique over conventional PCR assays.

Aggregatibacter actinomycetemcomitans↗

PubMed1998

Risk factors for HIV seropositivity in a sample of drug users in drug treatment in Ho Chi Minh City, Vietnam.

The article describes drug use behaviors, AIDS knowledge, risks for HIV infection, and HIV seroprevalence in drug users entering rehabilitation in Ho Chi Minh City, Vietnam. A cross-sectional, descriptive survey of all new entrants to a residential drug treatment center was conducted with linked HIV serology between July 1 and July 14, 1995. A total of 105 subjects participated: 101 men and 4 women. HIV serostatus was available for 88 subjects. Forty-seven percent (41 of 88 subjects) were HIV-positive. Median age of the subjects was 38 years. Mean length of injection drug use was 13.2 years (range, 1-27 years). The primary drug of injection was opium (96%), although 59% of subjects also injected "Western" drugs such as sedatives or tranquilizers. Eighty-two percent (86 of 105 subjects) correctly answered at least 7 of 10 AIDS knowledge questions, and only 28% (27 of 97 subjects) reported any needle sharing in the last 5 years. Seropositivity was associated with a history of previous treatment for drug abuse (p = 0.002), longer history of injecting drugs (p = 0.003), use of Western drugs (p = 0.03), and higher educational level (p = 0.05). Multivariate analysis found that the independent predictors of HIV seropositivity were history of previous treatment for drug abuse (p = 0.06) and longer history of injecting drugs (p = 0.05). Despite low levels of self-reported needle sharing and high levels of AIDS knowledge, HIV seroprevalence was high in this sample. The potential for epidemic spread of HIV in Vietnamese drug users is substantial. Risk-reduction programs and intense AIDS education projects targeting the population of drug users are necessary to control the AIDS epidemic in Vietnam.

Adult↗

PubMed1996

Risk indicators for periodontal disease in a racially diverse urban population.

A cross-sectional study of 117 subjects from a dental clinic serving a diverse population (i.e., Whites, African-Americans, Native-Americans, and Asians) was performed to evaluate risk indicators of periodontal disease. Gingival crevicular fluid (GCF) and subgingival plaque were taken at the same visit from 4 posterior sites of the most diseased sextant in each subject. Age, smoking packyears, beta-glucuronidase (beta G), neutrophil elastase (NE), myeloperoxidase (MPO), Fusobacterium nucleatum (F. nucleatum), and Porphyromonas gingivalis (P. gingivalis) were significantly (p < 0.05-0.005) correlated with attachment loss. Probing depth was significantly correlated with smoking packyears, beta G, NE, MPO, F. nucleatum and Prevotella intermedia (P. intermedia) (p < 0.05-0.005). Mean NE value of Whites was lower than the mean NE values of African-Americans, Native-Americans and Asians (p < 0.05). Whites had a lower mean beta G value compared to African Americans, and a lower mean MPO value compared to African Americans and Native Americans. The %s of patients positive for F. nucleatum, P. intermedia and Eikenella corrodens (E. corrodens) were higher in Native Americans compared to Whites. Step-wise multiple regression analysis was performed to construct models for the estimation of probing depth and attachment loss. The most parsimonious regression models which had the best R2 values included the following variables and accounted for the indicated % of variability: models 1 and 2: beta G, race, and F. nucleatum accounted for 50% of the variability in mean probing depth and 39% of the variability in a single site (first molar) for probing depth, respectively; model 3: age, beta G, and F. nucleatum accounted for 53% of the variability in mean attachment loss; model 4: age, NE, and F. nucleatum explained 35% of the variability in a single site (first molar) for attachment loss. The results suggest that age, race, smoking packyears, beta G, NE, MPO, F. nucleatum, P. gingivalis and P. intermedia are risk indicators for periodontal disease in this racially diverse urban population. Regression models which include multiple variables (i.e., demographic factors, GCF enzymes and periodontopathic bacteria) can be used to estimate periodontal disease status.

Adolescent↗

PubMed1996

Multiplex PCR using conserved and species-specific 16S rRNA gene primers for simultaneous detection of Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis.

Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis are strongly associated with periodontitis. However, little is known about their distribution in periodontally healthy individuals, because culturing techniques are not sufficiently sensitive. A modified multiplex PCR was developed to address that question. Our method uses two species-specific forward primers in combination with a single reverse primer. These primers target variable and conserved regions of the 16S rRNA gene. Sensitivity was determined by testing serial dilutions of A. actinomycetemcomitans and P. gingivalis cells. Primer specificity was tested against (i) six A. actinomycetemcomitans strains and four P. gingivalis strains, (ii) seven different species of oral bacteria, and (iii) supra- and subgingival plaque from 20 subjects. The multiplex PCR had a lower limit of detection of 2 A. actinomycetemcomitans and 30 P. gingivalis cells. Species-specific amplicons were obtained for all A. actinomycetemcomitans and P. gingivalis strains tested and did not occur with seven other bacterial species unless A. actinomycetemcomitans and P. gingivalis were added. Neither target species was detected in supragingival plaque; A. actinomycetemcomitans was detected in one subgingival specimen, and P. gingivalis was detected in another. When plaque samples were spiked with 10 A. actinomycetemcomitans cells and 100 P. gingivalis cells, species-specific amplicons were detected. These findings show our multiplex PCR to be highly sensitive and specific while allowing simultaneous detection of A. actinomycetemcomitans and P. gingivalis. This assay has potential applications in epidemiological studies, diagnosis, treatment planning, and monitoring of periodontal pathogens.

Aggregatibacter actinomycetemcomitans↗

PubMed1993

[Pleomorphic adenoma].

A clinical case involving a pleomorphous adenoma at a minor salivary gland of the palate is diagnosed and treated by the Department of maxillo-facial surgery at the Notre-Dame Hospital, in Montreal. The signs and symptoms of this adenoma are discussed together with the X-ray report and the histopathological examination. The treatment chosen is a surgical excision of the whole tumor, including the periosteum of the palate, followed by the installation of a prefabricated acrylic obturator.

Adenoma, Pleomorphic↗

PubMed1987

Reversible inhibition of cytosolic glucocorticoid receptors by mercurial agents. Application in the measurement of total and unoccupied receptors.

Recently developed "exchange assays" have been used to measure total cytosolic glucocorticoid receptor (GR) binding activity as compared to standard GR assays which measure unoccupied receptor. In the current study we modified these methods and extended the applications of such assays. Experiments defined the conditions whereby two sulfhydryl-binding agents, p-hydroxymercuribenzoate (PHMB) and mersalyl, completely inhibited binding of the glucocorticoid receptor to ligand in mouse renal cytosol. Reactivation of steroid-binding activity was restored by addition of dithiothreitol. The present study demonstrates 12% higher GR binding activity when this exchange assay is performed using saturated glucocorticoid-receptor complex, rather than standard cytosol. Combining the data from the standard and exchange mouse renal cytosolic GR assays, it was determined that, at physiologic tissue corticosterone levels, the respective mean concentrations of unoccupied, occupied, and total GR were 467, 89, and 556 fmol/mg cytosol protein. Measurement of receptor concentrations by the use of these methods permits precise experimental differentiation of factors which affect total, as well as unoccupied GR.

Animals↗

PubMedDate not supplied

Primary culture of polarized human salivary epithelial cells for use in developing an artificial salivary gland.

Therapeutic irradiation for head and neck cancer, and the autoimmune disease Sjogren's syndrome, lead to loss of salivary parenchyma. They are the two main causes of irreversible salivary gland hypofunction. Such patients cannot produce adequate levels of saliva, leading to considerable morbidity. We are working to develop an artificial salivary gland for such patients. A major problem in this endeavor has been the difficulty in obtaining a suitable autologous cellular component. This article describes a method of culturing and expanding primary salivary cells obtained from human submandibular glands (huSMGs) that is serum free and yields cells that are epithelial in nature. These include morphological (light and transmission electron microscopy [TEM]), protein expression (immunologically positive for ZO-1, claudin-1, and E-cadherin), and functional evidence. Under confocal microscopy, huSMG cells show polarization and appropriately localize tight junction proteins. TEM micrographs show an absence of dense core granules, but confirm the presence of tight and intermediate junctions and desmosomes between the cells. Functional assays showed that huSMG cells have high transepithelial electrical resistance and low rates of paracellular fluid movement. Additionally, huSMG cells show a normal karyotype without any morphological or numerical abnormalities, and most closely resemble striated and excretory duct cells in appearance. We conclude that this culture method for obtaining autologous human salivary cells should be useful in developing an artificial salivary gland.

Artificial Organs↗