Interleukin-8 gene expression and apoptosis induced by Salmonella Typhimurium in the presence of Bacillus probiotics in the epithelial cell.

AIMS: This study aimed to evaluate the effects of three Bacillus probiotics on Salmonella Typhimurium, and interleukin-8 (IL-8) gene expression in the co-culture of the Bacillus and the pathogen in vitro. METHODS AND RESULTS: Bacillus subtilis, Bacillus indicus and Bacillus coagulans were initially turned to spore and heat-inactivated forms. The cellular damages of the probiotics on the HT-29 cells were investigated individually and in combination with S. Typhimurium using 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and fluorescence assays. To extract cell free supernatants (CFS) of the probiotics, they were cultured in selective media. The inhibitory activity of CFSs were then assayed against the pathogen. The gene expression of IL-8 of the HT-29 cells was evaluated by real-time PCR in all the groups. The results showed that the CFSs of three probiotics could inhibit the growth of S. Typhimurium by more than 50%. Inhibitory effects of B. indicus and B. subtilis CFSs were related to the production of pepsin-sensitive compounds, except B. coagulans in which the high inhibitory effect was due to organic acids. The spores of the three probiotics and the heat-inactivated forms of B. subtilis and B. coagulans could reduce the cytotoxicity of S. Typhimurium. The cell viability also increased applying both forms probiotics against the pathogen. In all co-culture groups, the IL-8 gene expression induced by S. Typhimurium was reduced. CONCLUSIONS: The three Bacillus probiotics can be considered as proper candidates for the prevention and treatment of S. Typhimurium food poisoning. SIGNIFICANCE AND IMPACT OF THE STUDY: Applying probiotics as live bacteria is universally noted in foods. This study tried to discover the effects of Bacillus probiotics in the form of spore or even heat-killed bacteria against S. Typhimurium and evaluate ratio of IL-8 gene expression in cell culture. The most effective Bacillus probiotic will be recommended. This approach will help to use probiotics as nonvegetative cells in foods to fight gastrointestinal pathogens.

Early responses of periodontal ligament cells to mechanical stimulus in vivo.

Previous studies have indicated that human periodontal ligament cells undergo osteoblastic differentiation via the ERK pathway under mechanical stress in vitro. This study aimed to verify this principle in vivo. The right upper first molars of 25 anesthetized rats were loaded with constant forces of 0.1 N for up to 8 hrs. The untreated contralateral side served as a control. Paraffin-embedded sections were analyzed by immunohistochemistry for proliferating cell nuclear antigen (PCNA), runt-related transcription factor 2 (Runx2/Cbfa1), and phosphorylated extracellular signal-regulated kinases 1/2 (pERK1/2). In selected areas under tension, the proportions of Runx2-positive and pERK1/2-positive cells increased within 8 hrs of loading, whereas these proportions in selected areas under pressure were significantly lower than those in control teeth. Moreover, there were no significant changes in the number of PCNA-positive cells. Thus, mechanical stimulus up-regulates Runx2, and this regulation may be achieved via the ERK pathway.

[Numerical study of tension and strain distribution around rat molars]. / Numerische Untersuchung der Spannungs- und Verzerrungsverteilungen um Rattenmolaren.

A knowledge of the mechanical processes triggered in the bone and periodontal ligament (PDL) by orthodontic forces applied to a tooth is of decisive importance for an understanding of the subsequent remodelling around the tooth. To investigate these mechanical relationships, three-dimensional finite element (FE) models of the first lower molar in the rat were established. On the basis of digitized serial histological sections, these FE models were generated semi-automatically. Using various simplified geometrical variations, an appropriate FE model for the analysis of the stress and strain distributions was established. The numerical analyses were carried out under a mesially directed force of 0.1 N. Stress distributions in the bone and PDL showed a similar pattern, while strains in the bone were lower than in the PDL by a factor of 10-5. The data confirm the assumption that strain patterns in the PDL may be the key stimulus of bone remodelling.

Numerical simulation of the biomechanical behaviour of multi-rooted teeth.

The elastic properties of the periodontal ligament (PDL) in eight multi-rooted teeth were examined in a combined experimental and numerical study in six minipigs. The initial tooth movement of the mandibular primary molars surrounded by the periodontium was registered three-dimensionally (3D) in an optomechanical measuring system. The dissections were then embedded in resin and cut in transverse sections. Based on these sections, 3D finite element (FE) models were constructed and numerically loaded with the same force systems as used in the experiment. The material behaviour of the PDL registered in the experiment was non-linear and could be approximated with a bilinear parameter set consisting of two Young's moduli, E1 and E2, and one ultimate strain, epsilon12, separating both elastic regimes. When a deficient congruence existed between the experimental and numerical force/deflection curves the material parameters were varied to obtain a satisfactory congruence. The material behaviour determined for these specimens delivered mean values of E1 = 0.05 MPa, E2 = 0.18 MPa and epsilon12 = 6.4 per cent for the elastic behaviour of the multi-rooted minipig teeth. There was no significant difference in the material parameters determined for specimens with two, four or six roots. The results were in close agreement with the material parameters of the PDL, determined in previous investigations of single-rooted human and pig teeth.

Experimental and numerical determination of initial tooth mobility and material properties of the periodontal ligament in rat molar specimens.

The mechanical parameters of the periodontal ligament (PDL) in rat specimens were investigated in a combined experimental and numerical approach. Tooth mobility of the rat mandibular first molar was measured in vitro using a high precision experimental set-up. Finite element models (FEM) were developed, based on histological sections of the measured specimens, to simulate tooth mobility numerically under the same force systems as used in the experiment. Force/deflection curves from the measurements showed a significant non-linear behaviour of elastic stiffness of the PDL. A bilinear material parameter set was assumed to simulate tooth deflections. The numerical force/deflection curves were fitted to the experimental curves by repeatedly calculating theoretical tooth deflections and varying the parameters describing the non-linearity. Mean values of E1 = 0.15 MPa, E2 = 0.60 MPa and an ultimate strain of epsilon12 = 6.3 per cent were derived for the elastic behaviour of the rat PDL. Comparing fresh specimens and those frozen in a 0.9 per cent saline solution, differences between the measurements were significant. Using the agent, Periston, for freezing significantly reduced the deviation. The results indicated that strains in the PDL with a maximum of 14 per cent at the furcation were 10(4) times higher than strains in the bone, while the variability of stress values in both PDL and bone was not significant.