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Biomedical subjects

D A Chambers

Publications and source records attributed to D A Chambers.

At least 37 records · Page 2Linked to original sources
PubMed1991

Plasminogen activator in human periodontal health and disease.

Plasminogen activators, proteases associated with the fibrinolytic system, also play a major part in extravascular processes such as tissue remodelling, cell migration and activation of prohormones, growth factors and other proteases. It is likely that plasminogen activators participate in the pathophysiology of periodontal disease. Plasminogen activator has been identified in human gingival crevicular fluid in a concentration 100-fold greater than in plasma. The local activity of plasminogen activator in gingival tissues was examined and changes detected in its distribution in relation to the extent of disease. Frozen sections from human gingival biopsies were overlaid on fibrin-coated slides; tissue-type plasminogen activator activity was found in all samples. Focal activity was observed in healthy tissue, originating from the most superficial cells of the junctional epithelium. Biopsies of clinically healthy sites obtained 6 weeks after treatment for periodontitis also showed epithelial plasminogen activator activity localized to this area. In contrast, in diseased tissue the entire epithelium lining the periodontal pocket showed activity. This differential pattern of activity in health and disease is consistent with the hypothesis that plasminogen activator is a modulator of periodontal homeostasis.

Gingiva↗
PubMed1991

A longitudinal study of aspartate aminotransferase in human gingival crevicular fluid.

Previous studies have shown that aspartate aminotransferase (AST), an established serum marker for cardiac and liver damage in humans, appears in elevated concentrations in samples of gingival crevicular fluid (GCF) from ligated vs. non-ligated teeth in beagle dogs and in elevated quantities in cross-sectional GCF sampling, adjusted for collection time, from human sites with clinical signs of past or present periodontal disease as compared to healthy sites. This paper describes a longitudinal study in which AST was monitored quarterly over a 2-year period at 2 sites/tooth in 31 patients with mild to moderate adult periodontitis. In this study sample, 40 (2.6%) of 1536 sites exhibited confirmed loss of at least 2 mm of attachment during the 2-yr observation period. In comparison with healthy sites within the same patients, AST standardized to a 30-second collection interval (AST30) was elevated at these sites with new confirmed attachment loss, and at sites with past attachment loss or gingivitis in the absence of periodontitis. When both within- and between-patient variation were taken into account, observed odds-ratios associating enzyme with disease were higher for sites with new attachment loss (9-16 depending on test cut-point) than for sites with pre-study attachment loss (3-12), or gingivitis in the absence of periodontitis (5-8). AST in GCF is strongly related to human periodontal disease. The data are consistent with the hypothesis that the relationship is strongest during episodes of cumulative tissue breakdown, but the small numbers of sites with confirmed attachment loss during the study period, or with gingivitis in the absence of periodontitis, means that further clinical studies are necessary to clarify this issue.

Adult↗
PubMed1991

A cross-sectional analysis of aspartate aminotransferase in human gingival crevicular fluid.

Previous investigation has shown that the concentration of aspartate aminotransferase (AST), an established serum marker for cardiac and liver damage in humans, is significantly elevated in samples of gingival crevicular fluid (GCF) from ligated teeth in beagle dogs. This paper reports on a cross-sectional study of the relationships between AST in GCF and clinical indices of human periodontal disease in 60 patients with mild to moderate adult periodontitis. AST standardized to a 30-second collection interval (AST30) showed substantial (multiple regression R2 = 0.61) association with summary indices of patient disease status, modest association (partial R2 = 0.22) with tooth disease status within patient, and weaker (partial R2 = 0.12) but statistically significant association with site-to-site variation in disease at the same tooth. AST concentration showed modest (R2 = 0.30) between-patient relationship with clinical indices, but no clinically significant relationship with these indices between sites within patients, suggesting a rough proportionality between accumulated enzyme and GCF volume at sites with varying stages of disease. The relationship between GCF volume and probing depth also appears central to interpretation of enzyme assays. Clinical measures of past periodontitis and current inflammatory disease are cross-sectionally related to variation in AST30, across patients and sites within the same patient. Considerable residual variation, especially elevated AST30 in the absence of clear signs of disease, may result from varying levels of current disease activity, not reflected in clinical measures.

Adult↗
PubMed1991

Association of gingival crevicular fluid aspartate aminotransferase levels with histopathology during ligature-induced periodontitis in the beagle dog.

Previous investigations have shown a clear association between the presence of the enzyme aspartate aminotransferase (AST) in gingival crevicular fluid (GCF) and clinical evidence of periodontal disease in humans, as well as in the beagle dog model. This paper describes a 26-week study that uses the beagle dog model of ligature-induced periodontitis in which GCF-AST (corrected for collection time) was correlated with microscopic evidence of tissue destruction in the periodontium at the sites of fluid collection. GCF and clinical data were collected at baseline, at optimal gingival health, during gingivitis, and after ligation. A cross-mouth design was implemented so that six premolar teeth in each dog were ligated for periods up to five weeks. Formalin-fixed tissues from the sites of GCF collection were prepared for light microscopy and evaluated for the presence of epithelial ulceration, bone resorption, and inflammatory cell infiltration. The relationship between GCF-AST levels and microscopic findings was analyzed by calculation of sensitivity and specificity and by plots of Receiver Operating Characteristics. These data revealed a correlation between elevated enzyme concentration and microscopic evidence of disease activity. Taken together with human studies, these results provide support for the use of AST as a marker of periodontal disease progression.

Alveolar Bone Loss↗
PubMed1989

Molecular characterization of plasminogen activator in human supragingival plaque.

Extravascular participation of the serine protease plasminogen activator (PA) in tissue remodelling and cell migration may be relevant in the regulation of periodontal homeostasis and the pathogenesis of periodontal disease. The molecular nature of authentic PA in crevicular fluid has been characterized, and this study has sought to determine whether human supragingival plaque also contains PA; if so, of which molecular species and from what source. Thirty samples of supragingival plaque plaque from 10 individuals, extensively washed to remove adherent saliva, were all found by substrate analysis to have tissue-type PA (tPA) activity. Unstimulated parotid or mixed saliva also showed tPA activity, but submandibular saliva had no measurable PA activity. Freshly isolated plaque microbes cultured under aerobic or anaerobic conditions contained no PA activity (preliminary investigation). PA activity was restricted to individual epithelial cells suggesting that the origin of PA activity in human supragingival plaque is in part from plaque-adherent epithelial cells.

Adult↗
PubMed1987

Topographic distribution of Thy-1 positive cells in epithelial tissues of BALB/c mice.

Epithelial sheets prepared from murine oral epithelia (palate, lining mucosa, gingiva) and oesophagus contained dendritic and round Thy-1 positive (+) cells similar to those observed in epidermis by immunofluorescence microscopy. Bladder, intestine and tracheal epithelium did not contain such cells. Thus, cells bearing the cells-surface glycoprotein Thy-1, like Ia-antigen-bearing Langerhans cells, may be restricted to stratified squamous epithelia.

Animals↗
PubMed1987

Two-dimensional gel electrophoresis of dog crevicular fluid proteins.

The ligature-induced periodontitis model was used in beagle dogs to compare and contrast profiles of crevicular fluid (CF) proteins collected from gingivitis and periodontitis sites. The protein profiles of CF and serum were determined by 2-dimensional gel electrophoresis (2-D PAGE) using a silver stain. 2-D PAGE showed that CF contained proteins with molecular weight 16 K or less and many proteins with molecular weights between 64 K and 16 K in the isoelectric pH between approximately 5.8 and 6.8. The number of such proteins was greater in samples collected from the ligated (periodontitis) side compared to the non-ligated (gingivitis) side. Thus, analysis by 2-D PAGE revealed differences between CF samples from gingivitis and ligature-induced periodontitis sites. This study suggests that analysis of human CF by 2-D PAGE may be useful in diagnosis and investigation of the pathogenesis of periodontitis.

Animals↗
PubMed1986

Thy-1+ epidermal cells are not demonstrable in rat and human skin.

Recent studies have revealed the presence of a population of Thy-1+ epidermal cells in murine epidermis. These experiments were designed to determine whether analogous Thy-1+ cell populations occur in rat and human epidermis. Thy-1+ cells could not be demonstrated in epidermal sheets derived from rat and human skin or in epidermal cell lines, KB and A431. To date, Thy-1+ epidermal cells have been observed only in murine epithelia. The cellular equivalent of the murine Thy-1+ cell in other species remains elusive.

Adult↗
PubMed1985

The Thy-1 epidermal cell: perspective and prospective.

Recently a class of cells distinguished by the presence of the cell-surface protein, Thy-I, has been discovered in the epidermis. These cells constitute a heterogeneous population such that they may be dendritic or round, and may be derived from both mesenchymal and ectodermal tissue. Phenotypically, cells with the following characteristics have been observed: Thy-I +, Vim+; Thy-I+, Vim-; Thy-I+, Ker+; Thy-I+, Ker-; Thy-I+, asialo GMI+; Thy-I+, asialo GMI-. Thy-I+ epidermal cells do not appear to be T or B lymphocytes, macrophage/monocytes or melanocytes. The Thy-I+ epidermal cell can be studied in in vivo and in vitro systems. It would appear that skin as well as the immune system contain Thy-I+ and Ia+ cells. Such cells may be prerequisite for both systems to carry out their primary defense functions.

Animals↗
PubMed1984

Direct effects of minoxidil on epidermal cells in culture.

Minoxidil, a potent antihypertensive agent, induces generalized hypertrichosis when administered systemically, or localized hair regrowth when applied topically to sites of severe alopecia areata. The pharmacologic mechanisms by which minoxidil stimulates hair growth are unknown. This study was designed to examine whether minoxidil has direct effects on neonatal murine epidermal cells in culture. In the presence of minoxidil, cultures showed a marked dose-dependent second peak of DNA synthesis 8-10 days after culture initiation. In addition, two morphologically distinct cell types appeared. Indirect immunofluorescence staining with keratin-specific antibody revealed cytoplasmic keratin fibers, suggesting the epidermal origin of these cells. Our experiments demonstrate that minoxidil can affect epidermal cells in culture by altering their growth pattern and phenotypic appearance.

Animals↗
PubMed1984

Dynamics of Langerhans cells in genetically defined murine epidermal cell culture.

Unlike keratinocytes, Langerhans cells express both surface ATPase activity and Ia (HLA-DR) antigens. A well-characterized in vitro system containing Langerhans cells would be of great use in elucidating their functions. Thus, epidermal cell cultures derived from neonatal Balb/c mice were examined for the presence of Langerhans cells. Twenty-four hours after initiation of culture, ATPase- and Ia-positive cells were seen to be associated with cell aggregates. By day 3, Langerhans cells migrated on to the substratum and, as the cultures matured and stratified, were seen both in groups and as single cells for the duration of the cultures (day 14). During culture, although the total number of cells increased, the percentage of cells expressing Ia antigen and ATPase activity remained constant, suggesting that Langerhans cells increase in number during cell culture. Such a situation could arise from actual division of Langerhans cells during culture or from latent expression of Ia antigen and ATPase activity by pre-existing cells. This is the first study of the dynamics of Langerhans cells in a cell culture system and shows that Langerhans cells are present throughout the lifespan of the cultures.

Adenosine Triphosphatases↗
PubMed1984

Aspartate aminotransferase increases in crevicular fluid during experimental periodontitis in beagle dogs.

A ligature-induced periodontitis model employing the beagle dog was used to study the levels of aspartate aminotransferase (AST) in crevicular fluid before and after ligation. A significant increase in AST level occurred in crevicular fluid 2 weeks after ligation whereas no increase of enzyme was found in serum. Enzyme levels in crevicular fluid were 10- to 100-fold higher than in serum. Dental plaque did not appear to be the source of the enzyme. Since aspartate aminotransferase has been documented as a marker of cellular injury arising during heart disease and liver disease, this study suggests that aspartate aminotransferase, in like fashion, reflects cellular damage arising from active periodontal disease.

Animals↗
PubMed1984

Alopecia areata treated with topical minoxidil.

A 1% minoxidil topical solution was used to treat 48 patients with alopecia areata, ie, 24 patients with patchy disease and 24 patients with alopecia totalis or alopecia universalis. Twenty-five patients had terminal hair regrowth; in 11 of the 25 patients, it was cosmetically acceptable. No clinical features of the disease seemed to indicate the likelihood of hair regrowth. Hair regrowth began approximately two months after the initiation of treatment and was not uniformly well maintained after the treatment was terminated. One patient had an allergic contact dermatitis reaction to the minoxidil solution; no systemic side effects were seen. No notable systemic absorption was found in 18 adult patients. Effects on cutaneous blood flow or the immune system or some direct effect on hair follicles are possible mechanisms by which minoxidil therapy might stimulate hair growth.

Administration, Topical↗
PubMed1983

A deliberate hypotensive technique for decreasing blood loss during radical hysterectomy and pelvic lymphadenectomy.

Nitroglycerin was utilized in combination with general anesthesia in order to reduce mean arterial blood pressure with the objective of reducing operative blood loss in 26 consecutive patients undergoing radical hysterectomy and pelvic lymphadenectomy. This deliberate hypotensive technique added no morbidity and compared to a control group decreased the blood loss by 70%, shortened operating time by 29.5%, and decreased the percentage of patients requiring blood transfusions from 81% to 11.5%. The indications for controlled hypotension are still controversial and somewhat dependent upon the expertise of the anesthesia and surgery teams, availability of blood, and the risk of transfusion hepatitis. Cerebrovascular disease, myocardial ischemia, peripheral vascular disease, severe renal or hepatic disease, and hypovolemia are relative contraindications to deliberate hypotension.

Adolescent↗