Evidence of bidirectional flow in the sciatic vasa nervorum.

The purpose of this study was to determine whether bidirectional flow exists in the sciatic vasa nervorum. Images obtained using high-frequency color Doppler ultrasound in duplex imaging mode (Vevo 2100) were studied retroactively. In Fig. 1 (left panel; rat 1), the color Doppler signal and flow-velocity waveforms are indicative of pulsatile flow traveling towards (B) and away (C) from the probe. In the right panel (Fig. 1; rat 2), there appears to be three distinct vessels, reflective of non-pulsatile negative flow (D), and pulsatile positive (E) and negative (F) flows. These data confirm the presence of bidirectional arterial flow in the sciatic vasa nervorum. Investigating bidirectional flow in the intact whole nerve may be helpful in elucidating novel features of nerve blood flow control in healthy and diseased states.

System identification of baroreflex response to mild lower body negative pressure.

The effect of mild lower body negative pressure (LBNP) on baroreflex control of arterial blood pressure (ABP) has long been thought to affect cardiopulmonary baroreflex only, although recent studies have pointed out that arterial baroreceptors may be transiently unloaded too after the rapid onset of mild LBNP. This paper presents a spectral decomposition method for the black box identification of the contribution of arterial and cardiopulmonary baroreflexes to beat-by-beat variability of ABP in response to mild LBNP levels. The significant decrease of mean and diastolic arterial pressure and of the arterial baroreflex mediated contribution to overall variability of ABP which was found, suggested that the unloading of arterial baroreceptors may be reflected by an altered dynamic response of arterial baroreflex, too. In addition, arterial baroreflex mediated modulations were found to be the main player in the modulation of beat-by-beat fluctuations of ABP, while the role of cardiopulmonary baroreflex mediated responses appeared to contribute very little.