Microvascular research
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Microvascular research · Dec 2010
The evolving methodology to perform limb lymphoscintigraphy: from rest to exercise acquisition protocol.
In this technical report, prepared following the kind invitation of Professor D'Amore, we describe the evolution in the methodology of performing the limb lymphoscintigraphy. In details we described and compared the rest protocol with subcutaneous injection of the radio-colloids vs. the exercise intradermal injection protocol. The latter appears to be faster and easier to interpret, moreover allowing an adequate measurements of quantitative parameters of lymph drainage and distribution.
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Microvascular research · Dec 2010
Comparative StudyHyperaemic changes in forearm skin perfusion and RBC concentration after increasing occlusion times.
Tissue occlusion and the hyperaemic response upon reperfusion can be used as a tool to assess microvascular function in various vascular diseases. Currently, laser Doppler flowmetry (LDF) is applied most often to measure hyperaemic responses. In this study, we have applied tissue viability imaging (TiVi) and LDF to measure the change in red blood cell concentration and perfusion in the skin after occlusions of the forearm with increasing duration. ⋯ Furthermore, for both perfusion and RBC concentration, the maximum responses (perfusion: r(2)=0.59; RBC concentration: r(2)=0.78) and the recovery times (perfusion: r(2)=0.62; RBC concentration: r(2)=0.91) increase linearly with the duration of the occlusion. Maximum responses and recovery times were more reproducible for RBC concentration (as measured with TiVi) than for perfusion (as measured with LDF). These results show that perfusion and RBC concentration are related during post-occlusive hyperaemia and that TiVi can be used as a tool in the assessment of hyperaemic responses that has advantages in terms of reproducibility, sensitivity and ease of use.
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Microvascular research · Mar 2010
Validation of near-infrared laser speckle imaging for assessing microvascular (re)perfusion.
The present study was conducted to compare laser speckle imaging (LSI) with sidestream dark field (SDF) imaging (i.e., capillary microscopy) so as to validate the use of LSI for assessing microvascular (re)perfusion. For this purpose, LSI and SDF measurements were performed on the human nail fold during gradual occlusion of the upperarm circulation to modify nail fold perfusion under controlled circumstances. Additionally, a vascular occlusion test was performed to test the ability of LSI to detect rapid changes in tissue perfusion during reactive hyperemia and a hyperthermic challenge was performed to measure LSI perfusion at maximum functional capillary density. ⋯ The main finding was that changes in perfusion as measured by LSI correlated well with changes in capillary red blood cell velocities as measured by SDF imaging during controlled reduction of the (micro)vascular perfusion. It was further shown that LSI is capable of measuring tissue perfusion at high temporal and spatial resolution. In conclusion, LSI can be employed to accurately quantitate microvascular reactivity following ischemic and hyperthermic challenges.
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Microvascular research · Mar 2010
Rac GTPase is a hub for protein kinase A and Epac signaling in endothelial barrier protection by cAMP.
Elevation in intracellular cAMP level has been associated with increased endothelial barrier integrity and linked to the activation of protein kinase A (PKA). Recent studies have shown a novel mechanism of cAMP-mediated endothelial barrier regulation via cAMP-dependent nucleotide exchange factor Epac1 and Rap1 GTPase. This study examined a contribution of PKA-dependent and PKA-independent pathways in the human pulmonary endothelial (EC) barrier protection by cAMP. ⋯ SiRNA-induced Rac knockdown suppressed barrier protective effects of both PKA and Epac signaling in pulmonary EC. Intravenous administration of either 6Bnz, or 8CPT, significantly reduced lung vascular leak in the murine model of lung injury induced by high tidal volume mechanical ventilation (HTV, 30 ml/kg, 4 h), whereas combined treatment with 6Bnz and 8CPT showed no further additive effects. This study dissected for the first time PKA and Epac pathways of lung EC barrier protection caused by cAMP elevation and identified Rac GTPase as a hub for PKA and Epac signaling leading to enhancement of lung vascular barrier.