Platelets regulate ischemia-induced revascularization and angiogenesis by secretion of growth factor-modulating factors.

In ischemic tissue, platelets can modulate angiogenesis. The specific factors influencing this function, however, are poorly understood. Here, we characterized the complement anaphylatoxin C5a-mediated activation of C5a receptor 1 (C5aR1) expressed on platelets as a potent regulator of ischemia-driven revascularization. We assessed the relevance of the anaphylatoxin receptor C5aR1 on platelets in patients with coronary artery disease as well as those with peripheral artery disease and used genetic mouse models to characterize its significance for ischemia and growth factor-driven revascularization. The presence of C5aR1-expressing platelets was increased in the hindlimb ischemia model. Ischemia-driven angiogenesis was significantly improved in C5aR1-/- mice but not in C5-/- mice, suggesting a specific role of C5aR1. Experiments using the supernatant of C5a-stimulated platelets suggested a paracrine mechanism of angiogenesis inhibition by platelets by means of antiangiogenic CXC chemokine ligand 4 (CXCL4, PF4). Lineage-specific C5aR1 deletion verified that the secretion of CXCL4 depends on C5aR1 ligation on platelets. Using C5aR1-/-CXCL4-/- mice, we observed no additional effect in the revascularization response, underscoring a strong dependence of CXCL4 secretion on the C5a-C5aR1-axis. We identified a novel mechanism for inhibition of neovascularization via platelet C5aR1, which was mediated by the release of antiangiogenic CXCL4.

Comparison of Accuracy Between Pulp/Tooth Ratio and Tooth Coronal Index Methods for Dental Age Estimation Using Digital Panoramic Radiographs

ABSTRACT Objective: To evaluate the reliability and the accuracy of Tooth Coronal Index (TCI) and Pulp/Tooth Ratio (PTR) methods in dental age estimation using digital panoramic radiography. Material and Methods: In this cross-sectional study, 237 dental panoramic images were collected. The two methods (TCI and PTR) were applied to all left mandibular first and second molars based on inclusion and exclusion criteria. In order to analyze the acquired data, statistical methods were used. The estimated ages derived by exclusive formula were compared to the chronological age, and the error ranges for each indicator were measured to determine their accuracy. Results: There were negative correlations between PTR in the first molar (r=-0.89) and in the second molar (r=-0.788), as well as TCI in the first molar (r=-0.587) and in the second molar (r=-.242). In this study, we found that the Pulp/Tooth Ratio (PTR) accuracy rate for mandibular first and second molar teeth was 79.21% and 62.09 %, respectively, although the Tooth Coronal Index (TCI) value for these teeth was 34.45% and 5.85%. Conclusion: Pulp/Tooth Ratio and Tooth Coronal Index are potential age estimation indices. Although PTR was the more accurate one in our study. The results also demonstrated that indices related to the first molar tooth could be used to estimate age with greater accuracy and validity.

Photonic simultaneous frequency identification of radio-frequency signals with multiple tones.

A photonic approach to instantaneously identify frequency components of microwave signals with multiple tones is conceived and practically demonstrated. A mathematical model was first developed to predict the behavior of the system. Then the system operation was tested in practice. The system employs a double mixing technique that enables high-frequency measurement without the need for any high-frequency RF component or broadband photodetector. The system operation was demonstrated over a frequency range of 0.1-40 GHz. Frequency measurement of two simultaneous RF tones is demonstrated; however, the system has the potential to be expanded to measure a larger number of simultaneous RF tones. It also has the potential to operate over a wider frequency range.