Switching from healthy to unhealthy oxidative stress - does the radical type can be used as an indicator?

Ultraviolet (UV) radiation leads to the formation of free radicals, which may cause immunological modulations, skin aging or skin cancer. Sunlight exposure in the UVA region according to CIE 85 promotes almost 46% of radical formation in skin. A critical radical concentration characterized by the inversion of the domination of primary ROS (reactive oxygen species) to an excess of secondary LOS (lipid oxygen species) is proven for the spectral regions UV and or VIS light and is intended to be a marker for an imbalance in the redox system, which can no longer compensate harmful effects. To investigate whether this transition point is also universally valid for one spectral region, the radical formation during and after targeted UVA in situ-irradiation at 365 ± 5 nm and three different irradiances (31, 94 and 244 mW/cm2) was investigated in ex vivo porcine skin using x-band electron paramagnetic resonance (EPR) spectroscopy. The quantification was performed with the spin probe 3-(carboxy)-2,2,5,5-tetramethylpyrrolidin-1-oxyl (PCA), the spin trap 5,5-Dimethyl-1-Pyrroline-N-Oxide (DMPO) was used to characterize the radical species. Furthermore, the viability of the skin cells after irradiation was controlled by an MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay, skin integrity was examined by histological analysis. A significant dose dependence in the radical formation is given at higher irradiance. The transition point was detected in the range of 0.5 MED after irradiation with the highest irradiance. From this point on the proportion of LOS increases with increasing dose and the proportion of ROS decreases. After switching off the UVA irradiation no further quantitative changes were detected, but rapid changes in the radical pattern were observed demonstrating the importance of in situ irradiation during the use of spin traps. Heat-pre-stressed skin showed more LOS than ROS already at the beginning of the irradiation, leading to the assumption that the transition point to the distress-level has already been reached. In summary, a postulated transition point could be verified for the UVA spectral region using only one spin trap combined with in-situ irradiation. A certain degree of stress is necessary to detect an inversion of the ratio of ROS to LOS. This reversal indicates an imbalance in the redox status. However, at low intensities no changes at all in radical pattern appeared over time (dose), probably it can be compensated by adaptation processes of the skin.

Evaluation of an electromagnetic position tracking device for measuring in vivo, dynamic joint kinematics.

An electromagnetic position tracking device was evaluated to determine its static and dynamic accuracy and reliability for applications related to measuring in vivo joint kinematics. The device detected the position and orientation of small coiled sensors, maintained in an electromagnetic field. System output was measured against known translations or rotations throughout the measurement volume. Average translational errors during static testing were 0.1 +/- 0.04, 0.2 +/- 0.17, and 0.8 +/- 0.81 mm (mean+/-SD) for sensors 50, 300, and 550 mm away from the field generator, respectively. Average rotational errors were 0.4 +/- 0.31 degrees, 0.4 +/- 0.21 degrees, and 0.9 +/- 0.85 degrees (mean +/- SD) for sensors located at the same distances. Since we intended to use this system in an animal walking on a treadmill, we incrementally moved the sensors under various treadmill conditions. The effects of treadmill operation on translational accuracy were found to be negligible. The effects of dynamic motions on sensor-to-sensor distance were also assessed for future data collection in the animal. Sensor-to-sensor distance showed standard deviations of 2.6 mm and a range of 13 mm for the highest frequency tested (0.23 Hz). We conclude that this system is useful for static or slow dynamic motions, but is of limited use for obtaining gait kinematics at higher speeds.

Increment technique for extended Class V restorations: an experimental study.

The application and polymerization of composite or polyacid-modified resin composites in thin layers (increment technique) for filling cavities might partially compensate for the stress associated with polymerization shrinkage. In this study, the effect of this technique on the marginal integrity of Class V polyacid-modified composite restorations was investigated. In 30 extracted premolars, extended Class V cavities were prepared with the apical margin in root dentin and the coronal margin in enamel. They were then subjected to different treatments (10 teeth in each case): a) placement and polymerization of a thin resin composite layer (Dyract-Dyract PSA) in the coronal part of the cavity (plus one increment for the residual part) (Group 1), b) a thin layer at the apical part of the cavity (plus one increment for the residual part) (Group 2) and c) restoration of the entire cavity with one increment (bulk technique) (Group 3). Following three days' storage in water, the teeth were subjected to cyclic thermal loading (4 degrees C <-> 55 degrees C, 2,000 cycles). The percentages of defective bonding detected along the total length of the restoration margin were assessed before and after thermocycling by scanning electron microscopy. Following loading and thermocycling, no significant differences were found at the restoration-enamel interface. Fewer gaps were found at the restoration-dentin interface in Group 1 (18.7 +/- 25.7%) and Group 2 (20.5 +/- 22.8%) compared to the reference Group 3 (42.2 +/- 30.6%) (Mann-Whitney U test: p<0.05). Moreover, there were no significant differences between the two increment groups (1 and 2). In a significantly larger number of cases, a completely intact dentin restoration margin was detected when a coronal increment (Group 1) (44.4%) was used instead of the bulk technique (Group 3) (13.6%) (Chi square test: p<0.05). These results indicate that gap formation can be significantly minimized by using an increment technique to restore extended Class V cavities with polyacid-modified composite materials.

Attachment formation following replantation of cultured cells into periodontal defects--a study in minipigs.

Regeneration processes in the periodontium occur by the interaction of different cell populations. It is known that these cells are also capable of forming new periodontal tissue after culture in vitro. The present study investigated whether replanted cultured cells from the periodontium could contribute to attachment formation. Primary cell cultures from alveolar bone and periodontal ligament were obtained from 11 minipigs. Experimentally induced furaction and interdental defects (n = 168) were treated in groups: (a) flap surgery, replantation of alveolar bone cells, and covering of the defects with Teflon membranes (ABC group); (b) flap surgery, replantation of periodontal ligament cells and membranes (PLC group); (c) flap surgery, bone gelatin (carrier material) and membranes (BG group); (d) flap surgery and membranes (NBG group); (e) flap surgery (FS group); and (f) no treatment (NT group). The defects were clinically and histologically (polyfluorochrome labeling) assessed after 10, 30, and 90 days. In the ABC group, initial calcified tissue formation at the roots was apparent after only 8 days. Marked new formation of cementum and alveolar bone and the development of a new attachment were observed after 90 days. In the BG and the NBG groups, wound healing varied depending on membrane healing and the morphology of the defects, which led to significantly poorer and variable results. Similar results were found in the PLC group, although some defects showed extensive cementum and bone formation. Defects in the FS and the NT groups healed largely by epithelialization. The study shows that replantation of cultured alveolar bone cells leads to formation of new cementum and bone, which, in turn, leads to formation of a new attachment. It is likely that the cells stabilize the tissue formation in the defect or on the root surface in the early phase of wound healing and prevent epithelial downgrowth. Results also show that regeneration in the periodontium is determined by the availability of (precursor) cells capable of forming calcified tissues.

Formation of differentiated tissues in vivo by periodontal cell populations cultured in vitro.

The periodontium contains heterogeneous mesenchymal cell populations with various differentiation potentials. The capacity of these cells for tissue formation as well as the origin of their precursors are still not entirely defined. In this study, cells originating from different periodontal tissues were cultured in vitro, and tissue formation in vivo following orthotopic re-implantation was investigated. Cells were recovered from the alveolar bone and periodontal ligament tissue of six minipigs, and cultured cells were then grown on extracted dental roots from the homologous animals by means of co-culture in vitro. Each minipig received 2 roots covered with alveolar bone cells, 2 roots covered with periodontal ligament cells, and 2 control roots (without cells) implanted into palatal bone defects. Intravital fluorochrome labeling was performed, and two minipigs were histologically examined after 2, 4, and 12 weeks in each case. Controls showed widespread resorption and ankylosis, whereas roots covered with cultured periodontal cells exhibited tissue formation in vivo. Alveolar bone cells synthesized a calcified cellular tissue resembling cellular cementum, suggesting that cells within this population might differentiate into cementoblasts when reimplanted with a dental substrate in vivo. Periodontal ligament cells exhibited no calcified tissue formation in vivo, but cells synthesized a connective tissue with orientated fiber bundles attached to both host bone and root, resembling periodontal ligament.

[The synthesis of collagenous and noncollagenous proteins by cells from the periodontium]. / Synthese kollagener und nicht-kollagener Proteine durch Zellen aus dem Parodont.

Synthesis of collagenous and noncollagenous proteins by cells originating from the alveolar bone (AB-cells) and from the periodontal ligament (PDL-cells) of 8 minipigs was analyzed in primary cell cultures. Incorporation of 3H-proline into proteins recovered from cell extracts showed, that 13.7% of protein synthesized by AB-cells and 8.0% of protein synthesized by PDL-cells were collagens. In both cell lines relative amounts of collagens synthesized decreased significantly on subculturing (AB-cells: 9.3%, PDL-cells: 6.0%). Preincubation of 2nd subculture AB-cells with beta-glycerophosphate had no significant effect on collagen synthesis. Considering the fact that relative amounts of collagen recovered from cell extracts represent only 10-20% of collagen recovered from whole culture (i.e. cells and culture medium), we suggest that collagen synthesis is an important component of in vitro-protein synthesis of cells originating from the alveolar bone and the periodontal ligament.

Correlation between caries prevalence (DMFS) and periodontal condition (CPITN) in more than 2000 patients.

The CPITN (Community Periodontal Index of Treatment Needs) and DMFS (Decayed-Missing-Filled Surfaces) index were evaluated simultaneously to provide information on the mutual influences of periodontal disease and caries. With the aid of an electronic database system the data of the caries index and periodontal index of more than 2000 patients aged between 18 and 80 years were stored and calculated. As expected, the CPITN and DMFS values increased with age. When the CPITN was selected as a reference the DMFS was found to change with increasing CPITN. With the examination method used in this study no correlation could be established between the prevalence of caries and periodontal condition, although both conditions have a common aetiological factor: microbial plaque.

[Computed tomography of the heart. Technic for quantitative evaluation of the perfusion of the ischemic myocardial region. Experimental basis]. / Die Computertomographie des Herzens. Technik zur numerischen Bewertung der Perfusion ischämischer Myokardbezirke. Experimentelle Grundlagen.

A CT standard procedure has been developed in six series of experiments, using 62 anaesthetised dogs in order to quantitative relative blood flow through ischaemic heart muscle. Measurements of cardiac dynamics by means of contrast media were less strictly controlled. The use of the standardised procedures with contrast injections is necessary because of the variable perfusion and washout intervals of the contrast in normal and ischaemic myocardium.