Effect of caries preventive products on the growth of bacterial biofilm on titanium surface.

Fluorides may affect the oxide layer on titanium surface. Caries preventive mouthwashes or gels contain fluorides and are applied at low pH. The aim of the present work was to study whether various concentrations of fluoride at acidic pH cause changes in the surface structure on the polished region of Ti implants, and alter the adherence and colonization of bacteria. Commercially pure Ti grade 4 discs with a polished surface were treated with a mouthwash containing 0.025% fluoride, a gel containing 1.25% fluoride or a 1% aqueous solution of NaF (pH 4.5). The change of surface roughness of the samples and the colonization of Porphyromonas gingivalis strains were studied by scanning electron microscopy after 5 days of anaerobic incubation. The quantity of the bacterial protein was determined by protein assay analysis. Agents with high fluoride concentration at acidic pH increased the roughness of the Ti surface. A slight increase in the amount of bacteria was found on the surfaces treated with 1% NaF and gel in comparison with the control surface. This study suggested that a high fluoride concentration at acidic pH may hinder the development of a healthy transgingival epithelial junction on Ti implants, due to bacterial colonization.

Degradation of native feathers by a novel keratinase-producing, thermophilic isolate, Brevibacillus thermoruber T1E.

Strain T1E, isolated and identified as Brevibacillus thermoruber, and evolutionally distant from the known keratinolytic isolates, proved to have feather-degrading ability. During the 7-day fermentation period, T1E consumed 10 g/l native goose feathers as the sole source of carbon and energy at 50 degrees C under aerobic conditions. The isolate secreted a thermostable, keratinolytic protease, which exhibited activity optimally at pH 6.5, whilst it was inhibited at alkaline pH. The keratin cleavage and catabolism resulted in the accumulation of free aspartic acid and soluble peptides with maximum values of 31.6 and 720 mg/l, respectively. The majority of the fermentation end-products were found to be small oligopeptides with an average molecular mass of 2275 Da.

[Streptococcus mutans colonization on titanium surfaces treated with various fluoride-containing preventive solutions]. / A Streptococcus mutans kolonizációja különbözô fluoridot tartalmazó prevenciós oldatokkal kezelt titánfelszínen.

Fluoride is a reductive agent and may modify the oxide layer of titanium (Ti) in the transgingival region of dental implants. The low pH and the high fluoride concentration of prophylactic mouthwashes and gels (used in caries prevention) may play a role in this phenomenon. Our main goal was to examine whether changes on the surface structure of Ti caused by high fluoride concentration and acidic pH alter the adherence and the colonization of bacteria. Polished commercially pure Ti discs (CP grade 4, Camlog, Biotechnologies AG, Switzerland) were used in the study. Each sample was treated for 1 hour with one of the solutions: mouthwash containing 0.025% (250 ppm) fluoride, a gel containing 1.25% (12500 ppm) fluoride, and a solution of 1% NaF (3800 ppm fluoride), pH 4.5. The surface structure of the discs was analyzed by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The colonization of Streptococcus mutans was studied by scanning electron microscope (SEM) after a 5-day incubation period. The roughness of the treated sample surfaces (Ra), as revealed by AFM measurements, increased 1.3 times for the gel and the mouthwash, and approximately seven folds for the 1% NaF solution, as compared to the control surface. The high fluoride concentration and acidic pH of the gel and the 1% NaF solution resulted in a strong corrosion and a modification of the composition of the Ti surface. The XPS spectra showed the formation of a fluoride containing complex (Na2TiF6) bound strongly to the surface. A correlation was revealed between the roughness of the surface and thickness and maturity of the S. mutans bacterial colonies developed on the modified Ti surface. High fluoride concentration and acidic pH increased the roughness of the Ti surface. Bacterial biofilm colonization on this rough surface proved to be more mature. The amount of bacteria was increased due to the changes in the surface caused by fluoride treatment. The present study indicates that high fluoride concentration in an acidic pH environment may affect the development of a healthy transgingival epithelial junction on the Ti surface. This work was supported by the SIMI-NAS Project of the 5th FWP of the European Commission (Growth Program, GRD3-2001-61801), the Hungarian Ministry of Economy and the EC (GVOP-3.2.1.-2004-04-0408/3.0), the Hungarian Ministry of Health (ETT, 434/2006), and the Hungarian Scientific Research Fund (OTKA F-68440).

Cadmium-induced oxidative stress and antioxidative mechanisms in germinating Indian mustard (Brassica juncea L.) seeds.

Cadmium, known as a non-essential heavy metal, can cause oxidative stress in plants. In this study we tried to find out whether oxidative changes could be measured in the early stages of ontogenesis in Indian mustard (Brassica juncea L.) seeds exposed to Cd stress. Cadmium-caused oxidative stress and antioxidative responses were investigated with respect to both time- and concentration-dependence. Parameters that were measured were follows: total antioxidant capacity (ferric reducing ability of plasma (FRAP)), glutathione (GSH) content, level of lipid peroxidation (LP), total protein content, and glutathione-S-transferase (GST, EC 2.5.1.18) activity. Seeds were germinated in vitro at 0, 50, 100 and 200mg/LCd concentrations in dark for 12, 24, 48 and 96h. Oxidative stress occurred in the seeds due to Cd treatment, the level of LP was high at the beginning of the germination at all concentrations used, but it attenuated later on. FRAP showed concentration-dependent increase during 24h, but it decreased later on. GSH content was also elevated by increasing concentrations of Cd, which referred to the activity of non-enzymatic antioxidant system. The GST activity induced with germination only after 24h at the highest Cd concentration. The results show that FRAP is a suitable parameter with which to assess the antioxidant capacity of heavy metal-stressed germinating seeds.

Corrosive effects of fluoride on titanium: investigation by X-ray photoelectron spectroscopy, atomic force microscopy, and human epithelial cell culturing.

High fluoride (F(-)) concentrations and acidic pH impair the corrosion resistance of titanium (Ti). Effects of F(-)-containing caries-preventive prophylactic rinses, and gels on Ti were investigated by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Human epithelial cell attachment and proliferation were investigated by dimethylthiazol-diphenyl tetrazolium bromide (MTT) and protein content assays. Aqueous 1% NaF solution (3800 ppm F(-), pH 4.5) or high (12,500 ppm) F(-) content gel (pH 4.8) strongly corroded the surface and modified its composition. XPS revealed formation of a strongly bound F(-)-containing complex (Na(2)TiF(6)). AFM indicated an increase in roughness (R(a)) of the surfaces: 10-fold for the NaF solution and smaller for the gel or a mouthwash (250 ppm F(-), pH 4.4). MTT revealed that cell attachment was significantly increased by the gel, but was not disturbed by either the mouthwash or the NaF. Cell proliferation determined by MTT decreased significantly only for the NaF-treated samples; protein content assay experiments showed no such effect. This study indicates that epithelial cell culturing results can depend on the method used, and the adverse effects of a high F(-) concentration and low pH should be considered when prophylactic gels are applied by patients with Ti implants or other dental devices.

In vitro model of neurotoxicity of Abeta 1-42 and neuroprotection by a pentapeptide: irreversible events during the first hour.

The cell biology of Alzheimer's disease (AD) is characterized mainly by the neurodegeneration caused by the beta-amyloid (Abeta) peptides and by the formation of neurofibrillary tangles. The initial events of neurodegeneration in the brain tissue include synaptic dysfunction and axonopathy. Abeta-induced axonopathy and neurite degeneration were studied in vitro on differentiated human-derived neurotypic SH-SY5Y cells. Different methods were used to investigate the mechanism of action of aggregated Abeta on neuroblastoma cells. Abeta 1-42 aggregated for 1 h induced irreversible changes in the neurite morphology. Change of tau hyperphosphorylation and cell viability (cytoplasmic redox state and active membrane uptake) was irreversible during the first hour after the addition of Abeta 1-42 to the cells. These rapid events indicate that Abeta might induce neurodegeneration even at an early stage of Abeta-cell contact. A novel pentapeptide LPYFD-amide, an analog of Soto's LPFFD, significantly decreased neurite degeneration, tau aggregation, and cell viability reduction induced by Abeta 1-42.