Abstract
Pulse wave velocity (PWV) is a clinically interesting parameter associated to cardiac risk due to arterial stiffness, generally evaluated by the time that the pressure wave spends to travel between two arbitrary points. Optic sensors are an attractive instrumental solution in this kind of time assessment applications due to their truly non-contact operation capability, which ensures an interference free measurement. On the other hand, they can pose different challenges to the designer, mostly related to the features of the signals they produce and to the associated signal processing burden required to extract error free, reliable information. In this work we evaluate two prototype optical probes dedicated to pulse transit time (PTT) evaluation as well as three algorithms for its assessment. Although the tests were carried out at the test bench, where "well behaved" signals can be obtained, the transition to a probe for use in humans is also considered. Results demonstrated the possibility of measuring pulse transit times as short as 1 ms with less than 1% error.

Abstract
The present work proposes a new device for local pulse wave velocity (PWV), by using an innovative configuration of a double piezoelectric (PZ) sensor probe. PWV is assessed in one single location and involves the determination of time delay, between the signals acquired simultaneously by two PZs, 23 mm apart. The double probe (DP) is characterized in a dedicated test bench system, where two main studies were carried out. In the first one, the impulse response (IR) for each PZ sensor is determined and evaluated through the deconvolution method. In the second one, DP time resolution is estimated from a set of time delay algorithms and compared with the reference values, obtained through the signals of two pressure sensors. Results demonstrate the effectiveness of the inferred IRs in deconvolution purposes and the possibility of measure higher PWV values (approximate to 19m/s), through the DP, with an error less than 10%.

Abstract
The problem of using a piezoelectric (PZ) probe to non-invasively measuring the pressure wave propagation through a fluid contained in an elastic tube is considered in this paper. In particular, we describe a probe system designed to non-invasively reproduce the morphology of the pulsatile arterial pressure waveform (APW). The study is focused in three main issues: the mechanical interface that transmits the forces associated to the distension of the wall of the tube to the sensor, the electronic conditioning circuit and the methods to assess the global accuracy of the system. The circuit, incorporates a, new to our knowledge, baseline restorer (BLR) that contributes to maintaining a stable (non-floating) baseline of the cardiac pressure pulses, making real-time observations more effective. Identification and correction of the systematic errors, responsible for deviations of the correct output morphology, are also discussed and tested for different waveforms. To assess the performance of the probe a special purpose test bench was developed that can originate an arbitrarily shaped pressure wave and launch it through a silicone-rubber tube. Finally, preliminary results, taken at the carotid site of a set of human volunteers, are shown. The probe can be incorporated in a collar, and its pulse waveforms exhibit high intra-patient repeatability. It has the potential of being used as an alternative to costly techniques such as ultrasound or applanation tonometry. The root mean square error (RMSE) of the probe when reproducing cardiac-like pressure waveforms yielded a value of 1.8 +/- 0.22%.

Abstract
We developed and tested the performance of a new wavelet based algorithm for Augmentation Index (AIx) determination. The evaluation method relies on reference cardiac-like pulses that are synthesized using a weighted combination of exponentially shaped sub-pulses that represent the three main components of real pulses: the systolic stroke, its reflected replica and the carotid reservoir or windkessel effect. The pulses are parameterized so as to reproduce the main types of cardiac waveforms. The values of AIx yielded by the new algorithm are compared with the ones computed directly from the synthesized waveform and with the values produced by standard Probability Density Function (PDF) analysis.

Abstract
An arterial pressure waveform recorder and analyser based on a Microchip PIC microcontroller (mu C), dsPIC33FJ256GP710 is described in this article. Our purpose is to develop a dsPIC based signal monitoring and processing system for cardiovascular studies, specially dedicated to arterial pressure waveform (APW) capture. We developed a piezoelectric (PZ) probe designed to reproduce the APW from the pulsatile activity taken non-invasively at the vicinity of a superficial artery. The advantages in developing a microcontroller based system show up in decreasing the associate cost, as well as in increasing the functionality of the system. Based on a MathWorks Simulink platform, the system supports the development and transfer of program code from a personal computer to the microcontroller, and evaluation of its execution on rapid prototyping hardware. Results demonstrate that embedded system can be an alternative to be used in autonomous cardiovascular probes. Although additional studies are still required, this probe seems to be a valid, low cost and easy to use alternative to expensive and hard to manipulate devices in the market.

Abstract
Diabetic retinopathy (DR) is the leading cause of blindness in adults. In diabetes, there is activation of microglial cells and a concomitant release of inflammatory mediators. However, it remains unclear how diabetes triggers an inflammatory response in the retina. Activation of P2 purinergic receptors by adenosine triphosphate (ATP) may contribute to the inflammatory response in the retina, insofar as it has been shown to be associated with microglial activation and cytokine release. In this work, we evaluated how high glucose, used as a model of hyperglycemia, considered the main factor in the development of DR, affects the extracellular levels of ATP in retinal cell cultures. We found that basal extracellular ATP levels were not affected by high glucose or mannitol, but the extracellular elevation of ATP, after a depolarizing stimulus, was significantly higher in retinal cells cultured in high glucose compared with control or mannitol-treated cells. The increase in the extracellular ATP was prevented by application of botulinum neurotoxin A or by removal of extracellular calcium. In addition, degradation of exogenously added ATP was significantly lower in high-glucose-treated cells. It was also observed that, in retinal cells cultured under high-glucose conditions, the changes in the intracellular calcium concentrations were greater than those in control or mannitol-treated cells. In conclusion, in this work we have shown that high glucose alters the purinergic signaling system in the retina, by increasing the exocytotic release of ATP and decreasing its extracellular degradation. The resulting high levels of extracellular ATP may lead to inflammation involved in the pathogenesis of DR. (C) 2008 Wiley-Liss, Inc.