Dynamic viscoelastic properties, water absorption, and solubility of home reliners.

Scant rheological information is available regarding home reliners (liner type denture adhesives). We evaluated 6 different home reliners in regard to their viscoelastic properties, water absorption and solubility. Dynamic viscoelastic properties and changes over time were determined using a dynamic viscoelastometer, while weight changes, absorption, and solubility during immersion in water were also investigated. We found that the dynamic viscoelasticity of the tested home reliners was sensitive to changes in frequency, while the materials used had nearly no elasticity and exhibited viscous behaviors. They showed a dramatic change in viscoelastic properties and increase in weight after approximately 1 day of water immersion. A considerably high percentage of water absorption was also observed. From the viewpoint of dynamic viscoelastic properties and durability, our results indicate that the tested home reliners would not be suitable for improvement of ill-fitting dentures.

Comprehensive analysis of chemotactic factors for bone marrow mesenchymal stem cells.

To understand which growth factors/cytokines can affect migration of mesenchymal stem cells (MSCs) to injured tissues, we compared the effects of many (26) growth factors/cytokines on the migration activity of rabbit and human MSCs using a microchemotaxis chamber. Among them, platelet-derived growth factor (PDGF)-BB, PDGF-AB, epidermal growth factor (EGF), HB-EGF, transforming growth factor (TGF-alpha), insulin growth factor (IGF-I), hepatocyte growth factor (HGF), fibroblast growth factor (FGF-2), and thrombin consistently enhanced the migration of rabbit and human MSCs at appropriate concentrations. PDGF-BB showed the greatest effect on migration. Various combinations of these factors further enhanced the migration of MSCs, whereas combinations of factors that shared common cell-surface receptors did not induce the additive stimulation. On the other hand, some combinations, including that of FGF-2 or thrombin with PDGF-BB, suppressed the migration activity of MSCs. These findings suggest that combinations of growth factors are important to eliciting the maximal chemotactic effect. The factors that induced the migration of MSCs also enhanced their proliferation, suggesting that migration and proliferation can take place simultaneously. The above factors were also effective in stimulating the migration of fibroblasts, but thrombin alone selectively enhanced the migration of MSCs, suggesting that thrombin is useful to stimulate migration of MSCs without migration of fibroblasts.

In vitro mechanisms of interleukin-8-mediated responses of human gingival epithelial cells to Candida albicans infection.

Oral epithelial cells significantly influence host inflammatory responses against Candida albicans in oropharyngeal candidiasis. We sought to elucidate the pattern of interleukin-8 (IL-8) expression by oral epithelial cells, which may function as an early innate immune system mediator during C. albicans infection. Primary human gingival epithelial cells (HGECs) were co-cultured with either viable or heat-killed C. albicans or fungal-derived substances, such as fungal secretion, fungal extracted proteins, and alpha-mannan. In vitro cell injury due to viable C. albicans was detectable by an adenosine triphosphate-based assay after 12h of infection. Prior to the detection of cell injury, HGECs clearly increased production of interleukin-1 alpha (IL-1alpha) and IL-8 in response to C. albicans infection, as determined by enzyme-linked immunosorbent assay and real-time reverse transcription PCR. High concentrations of a suspension of heat-killed yeast and all fungal-derived substances examined also stimulated IL-8 production by HGECs. Incubation with neutralizing anti-IL-1alpha or anti-intercellular adhesion molecule-1 (ICAM-1) monoclonal antibodies (mAb) significantly inhibited C. albicans-induced IL-8 production. Use of mAbs against both IL-1alpha and ICAM-1 produced a more significant combined inhibitory effect on the IL-8 production than either mAb alone. These findings indicate that HGECs synthesize increased levels of IL-1alpha and IL-8 in response to viable C. albicans before cell injury is manifested. Fungal cell-wall components, alpha-mannan, and fungal protein extracts are all sufficient to increase IL-8 production. The molecular mechanisms governing the IL-8 response of HGECs to C. albicans infection likely involve multiple converging signal transduction pathways, including those mediated by IL-1alpha and ICAM-1 activation.

[Candida adherence and biofilm formation on oral surfaces].

Candida albicans is the most common fungal opportunistic pathogen in humans. The AIDS epidemic, improved life-sustaining therapy, and aggressive anticancer therapy have contributed to a rise in the number of severely immunocompromised patients. This has led to an increase in oral and systemic fungal infection. Several factors, such as adherence, persistence, dimorphism, germ tube formation, and/or contact sensing, phenotypic switching, interference with the host defense system, synergism with bacteria, and the production of hydrolases or other metabolites, have been proposed to be virulence factors of this fungus. Among these virulence factors, adherence and persistence are thought to be the most important, since the colonization and subsequent biofilm formation of oral surfaces may serve as a reservoir for disseminated infections, such as aspiration pneumonia and gastrointestinal infection. In the review, we summarized the factors involved in the Candida albicans biofilm formation.

Compatibility of tissue conditioners and dental stones: effect on surface roughness.

STATEMENT OF PROBLEM: Although the primary use of tissue conditioners is to treat abused mucosa, these materials are also frequently used as functional impression materials. No information was identified on the effect that these materials may have on the surface of the resultant dental stone cast. PURPOSE: This study evaluated the compatibility of 3 tissue conditioners with dental stones and changes in surface conditions over time. MATERIAL AND METHODS: Three tissue conditioners (COE-comfort, Soft-conditioner, and Visco-gel) and 4 dental stones (Capstone DF, New Plastone, Die Stone, and New Fujirock) were evaluated. One impression material (Examixfine) was used as a control. Tissue conditioner disks were made by pouring freshly mixed material into a polypropylene container, pressing the material down with a glass plate, and then removing the plate 2 hours later. The disks were then stored in distilled water for 0 or 24 hours, or 3, 7, or 14 days. Subsequently, each dental stone was mixed and poured over the top of each disk and allowed to remain for 60 minutes. Twenty-five disk-shaped specimens, 18 x 2 mm, for each tissue conditioner/stone cast combination were prepared. Mean surface roughness (Ra) values of the dental stone casts made from the tissue conditioners were determined using a profilometer. Five measurements for each specimen were made. Data were analyzed with 1- and 3-way analysis of variance and the Student-Newman-Keuls test (alpha=.05). Detail reproduction was also determined using a ruled test block, as specified in ISO specification 4823. RESULTS: Contribution ratios determined by 3-way analysis of variance indicated that the surface roughness values were significantly more influenced by the time of immersion in water ( P <.0005, contribution ratio rho=37%), than the type of tissue conditioner ( P <.0005, rho=19%) or dental stone used ( P <.0005, rho=1%). The best surface quality was obtained with a New Fujirock cast (0.81 +/- 0.06 microm), followed by New Plastone (0.83 +/- 0.12 microm) and Die Stone (0.85 +/- 0.05 microm) casts, in combination with Visco-gel without immersion in water, and those were nearly equivalent in surface roughness to a Die stone cast from Examixfine. The surface roughness values of all specimens, especially the COE-comfort/stone cast combinations, significantly increased with tissue conditioner immersion time ( P <.0005). Visco-gel tended to produce a better surface quality during the test periods than the other materials. All stone casts made from the tissue conditioners not immersed in water reproduced 20-microm or 50-microm lines, while the detail diminished over time with immersion. CONCLUSION: The type of tissue conditioner, and especially immersion time, had a significant effect on the surface quality of dental stone casts. The type of dental stone used is less important.

Intercellular adhesion molecule 1-dependent activation of interleukin 8 expression in Candida albicans-infected human gingival epithelial cells.

Increased induction of interleukin 8 (IL-8) and intercellular adhesion molecule 1 (ICAM-1) by oral epithelial cells may play a role in the host defense mechanism in oropharyngeal candidiasis; however, little is known about the expression feature of these molecules on human gingival epithelial cells (HGECs) during Candida albicans infection. In this report we present evidence that neutralization with antibody against ICAM-1 inhibited both the adherence of C. albicans to HGECs and the Candida-induced production of IL-8, suggesting a role for ICAM-1 in recognition and signaling in HGECs to express IL-8 upon infection with C. albicans.

Rhythmic expression of DEC1 and DEC2 in peripheral tissues: DEC2 is a potent suppressor for hepatic cytochrome P450s opposing DBP.

The mammalian master molecular clock consisting of several clock gene products in the suprachiasmatic nucleus (SCN) drives circadian rhythms in behaviour and physiology. Molecular clocks consisting of the same components also exist in various peripheral organs. DEC1 and DEC2, basic helix-loop-helix transcription factors, were recently reported to be involved in the central clock in the SCN. We examined the expression profile of DEC1 and DEC2 in the periphery and their roles in the regulation of oscillating target genes in the liver. Levels of DEC1 and DEC2 mRNA exhibited a day-night variation in various peripheral tissues of rats. In the liver, their expression was high during the subjective night. Transfection assays showed that DEC2, but not DEC1, suppressed the transcription of the cholesterol 7alpha-hydroxylase gene (CYP7A), overwhelming the potent enhancement by D-site binding protein (DBP). Electrophoretic mobility shift assays indicated that DEC2 binds to the E-box (CACATG) at the -219/-214 region of CYP7A. The transcriptional activities of the other sterol metabolizing cytochrome P450s (Cyps), CYP8B and CYP51, were also suppressed by DEC2 but not DEC1. DEC2, but not DEC1, works as a direct output mediator that transmits the circadian signals to the hepatic functions, including the CYP7A, CYP8B, and CYP51 expression.

Lectins induce resistance to proteases and/or mechanical stimulus in all examined cells--including bone marrow mesenchymal stem cells--on various scaffolds.

Transplantation of bone marrow mesenchymal stem cells (MSC), chondrocytes, osteoblasts, or muscle cells promotes regeneration. However, these cells adhere poorly to some scaffolds--depending upon the scaffold material--and are often damaged by proteases or mechanical stimuli at site of transplantation. We found, however, that MSC, chondrocytes, and osteoblasts--along with some other cells--that were exposed to phaseolus vulgaris erythroagglutinin (PHA-E) or concanavalin A (ConA) increased their adhesion capacity on plastic tissue culture dishes and on plates of hydroxyapatite, titanium and poly-DL-lactic-co-glycolic acid (PLGA), and that these cells, moreover, built up resistance to proteases and/or mechanical stimuli. Thus, lectins may have great potential in tissue engineering and cell therapy.