| 1. |
- Dubniks, Maris, et al.
(författare)
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Change in plasma volume from a state of hyper-, normo- or hypovolemia with or without noradrenalin infusion in the rat.
- 2008
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Ingår i: Microvascular Research. - : Elsevier BV. - 1095-9319 .- 0026-2862. ; 76, s. 75-79
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Tidskriftsartikel (refereegranskat)abstract
- Fluid substitution is important in critically ill patients to maintain normovolemia, but there is always a risk that the treatment is too aggressive resulting in fluid overload, or is insufficient with maintenance of hypovolemia. The present study on the rat aims at evaluating the change in plasma volume after 2.5 h from a state of hyper- and hypovolemia. The analysis was made without and with noradrenalin infusion, based on the fact that noradrenalin infusion is a common drug to maintain an adequate arterial pressure, and noradrenalin may induce transcapillary filtration. Plasma volume was determined at baseline and at the end of the experiments with a (125)I-albumin tracer technique. Arterial and central venous pressure, and urine output were recorded. We showed that induction of hypervolemia with a 5% albumin solution (15 ml/kg) resulted in successive loss of plasma volume, which was aggravated with noradrenalin infusion. Hypovolemia induced by hemorrhage (15 ml/kg) resulted in transcapillary absorption, an absorption almost abolished during noradrenalin infusion. There was no plasma volume loss in the sham group. Urine output was higher under hypervolemia than under normovolemia, which in turn was higher than under hypovolemia. We conclude that hypervolemia induces plasma volume loss, which is aggravated by noradrenalin infusion. The compensatory absorption effect after hemorrhage is counteracted by noradrenalin. The results can be explained by differences in hydrostatic capillary pressure via alterations in arterial and venous pressure, according to the 2-pore theory of transcapillary fluid exchange.
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| 2. |
- Freccero, Carolin, et al.
(författare)
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The influence of wavelength and probe configuration on findings of a skin vasoconstriction test when using laser Doppler perfusion devices.
- 2006
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Ingår i: Microvascular Research. - : Elsevier BV. - 1095-9319 .- 0026-2862. ; 71:Jan 3, s. 64-67
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to establish the degree to which a standardized test based on laser Doppler blood flow measurement is dependent on the particular equipment set-up being used. For this purpose, we examined finger skin blood flow with laser Doppler instruments in 20 healthy subjects. In laser Doppler perfusion monitoring (LDPM), we used a custom-made probe with two detecting fibers placed 0.25 and 1.2 min from the illuminating fiber, respectively, and two laser Doppler perfusion imagers (LDPI) with a wavelength of 632.8 nm and 780 rim, respectively. Warming of the hand was achieved with a Peltier element, and reflex vasoconstriction was induced by immersing the other hand for 3 min into a water bath kept at 15 degrees C. As a measure for the change in skin blood flow, a vasoconstriction index (VAC: cooling/before cooling) was calculated and used for the comparison of the different devices. VAC values gathered around 0.6 for all devices. However, LDPI with a wavelength of 632.9 nm showed a slightly higher VAC index, and the difference was significant. We conclude that using a standardized test is the most appropriate for monitoring changes in blood flow rather than recording and comparing discrete values in intermittent recordings. Although a difference was noted when comparing the devices, different fiber separations and wavelengths seem then to be of little consequence. (c) 2005 Published by Elsevier Inc.
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| 3. |
- Fredriksson, Ingemar, et al.
(författare)
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Measurement depth and volume in laser Doppler flowmetry
- 2009
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Ingår i: Microvascular Research. - : Elsevier BV. - 0026-2862 .- 1095-9319. ; 78:1, s. 4-13
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Tidskriftsartikel (refereegranskat)abstract
- A new method for estimating the measurement depth and volume in laser Doppler flowmetry (LDF) is presented. The method is based on Monte Carlo simulations of light propagation in tissue. The contribution from each individual Doppler shift is calculated and thereby multiple Doppler shifts are handled correctly. Different LDF setups for both probe based (0.0, 0.25, 0.5, and 1.2 mm source-detector separation) and imaging systems (0.5 and 2.0 mm beam diameter) are considered, at the wavelengths 543 nm, 633 nm, and 780 nm. Non-linear speckle pattern effects are accounted for in the imaging system setups. The effects of tissue optical properties, blood concentration, and blood oxygen saturation are evaluated using both homogeneous tissue models and a layered skin model. The results show that the effect on the measurement depth of changing tissue properties is comparable to the effect of changing the system setup, e.g. source-detector separation and wavelength. Skin pigmentation was found to have a negligible effect on the measurement depth. Examples of measurement depths are (values are given for a probe based system with 0.25 mm source-detector separation and an imaging system with a 0.5 mm beam diameter, respectively, both operating at 780 nm): muscle - 0.55/0.79 mm; liver - 0.40/0.53 mm; gray matter - 0.48/0.68 mm; white matter - 0.20/0.20 mm; index finger pulp - 0.41/0.53 mm; forearm skin - 0.53/0.56 mm; heat provoked forearm skin - 0.66/0.67 mm.
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| 4. |
- Henricson, Joakim, et al.
(författare)
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Assessment of microvascular function by study of the dose‐response effects of iontophoretically applied drugs (acetylcholine and sodium nitroprusside) : Methods and comparison with in vitro studies
- 2007
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Ingår i: Microvascular Research. - : Elsevier BV. - 0026-2862 .- 1095-9319. ; 73:2, s. 143-149
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Tidskriftsartikel (refereegranskat)abstract
- Current knowledge about vascular function stems mainly from pharmacological in vitro studies using mounted vascular strips on a strain gauge. We know of no paper that has systematically examined the possibility of assessing the conventional dose–response effects of iontophoresis and laser Doppler investigation of vasoactive substances and compared those relations to data obtained from strips mounted on a strain gauge. We used the vasoactive substances acetylcholine (endothelium dependent) and sodium nitroprusside (endothelium independent) and an antagonist (atropine) to enable further investigations in the receptor physiology of iontophoresis. Dose–response curves from the iontophoresis experiments showed close similarity to those obtained by vascular strips mounted on a strain gauge. The coefficient of variation (CV) of the dose–response factors found in iontophoresis (both inter and intra experimental variability) was low. The iontophoretic effective dose of 50% (ED50) for acetylcholine and nitroprusside had only CVs of 25% and 26%, respectively, compared with 71% and 77% for the vascular strips. Acetylcholine-induced response was antagonized by iontophoresis of atropine. Contrary to expectations, this antagonism was not competitive. The results show that iontophoresis in combination with laser Doppler technology produces reproducible and reliable dose–response curves that picture the vascular effects of vasoactive drugs.
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| 5. |
- Karlander, Lars-Erik, 1950-, et al.
(författare)
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Acidosis in muscle tissue distal to vascular contusion despite unchanged global blood flow in rats : An uncoupling of microvascular blood flow and metabolism?
- 2005
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Ingår i: Microvascular Research. - : Elsevier BV. - 0026-2862 .- 1095-9319. ; 70:1-2, s. 111-115
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Tidskriftsartikel (refereegranskat)abstract
- Studies using a contusion trauma model have shown that the femoral artery of the rat remains patent in 85% despite a severe vessel injury. A significant increase in tissue oxygenation (PtO2) has been found despite only a minor effect on blood flow (<20% decrease) on the muscle surface distal to the injury indicating a disturbed relationship between microvascular blood flow and metabolism. The aim of the present study was to further study the interplay between microvascular blood flow and metabolism within the distal muscle using an ethanol clearance technique (blood flow) in conjunction to the determination of an ischemia marker (lactate) by use of microdialysis. Although skeletal muscle blood flow remained unaltered as assessed by ethanol clearance, skeletal muscle lactate levels increased significantly (P < 0.001) post-trauma in both legs. The increase was initially higher, faster and the increase over time larger in the trauma leg as compared to the control leg (P < 0.001). These findings indicate a systemic effect of the trauma. Further, it suggests a functional impairment of the relationship between microvascular blood flow and/or muscle metabolic processes when the trauma is directed towards the supplying blood vessel. The reason for this anaerobic insult as found in this study compared to the presence of a local increase in PtO2 in the trauma leg as shown in our previous study is suggestive of an microvascular blood flow and tissue metabolism uncoupling. © 2005 Elsevier Inc. All rights reserved.
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| 6. |
- Laschke, Matthias, et al.
(författare)
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The Rho-kinase inhibitor Y-27632 inhibits cholestasis-induced platelet interactions in the hepatic microcirculation.
- 2009
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Ingår i: Microvascular Research. - : Elsevier BV. - 1095-9319 .- 0026-2862. ; 78, s. 95-99
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Tidskriftsartikel (refereegranskat)abstract
- Bile duct obstruction is associated with hepatic accumulation of leukocytes and liver injury. Emerging data suggest that platelets may play an important role in tissue damage and inflammation. Herein, we characterized the platelet response in cholestatic liver injury and evaluated the role of Rho-kinase signaling. For this purpose, C57BL/6 mice were treated with the Rho-kinase inhibitor Y-27632 (10 mg/kg) and vehicle before undergoing bile duct ligation (BDL) for 12 h. Platelet rolling and adhesion, formation of platelet aggregates as well as microvascular perfusion in the liver were analyzed using intravital fluorescence microscopy. Liver damage was monitored by measuring serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Administration of Y-27632 reduced the BDL-associated increase of ALT and AST by 95% and 89%, respectively. The inhibition of Rho-kinase also reduced cholestasis-induced platelet rolling and adhesion by more than 46% and 73% in postsinusoidal venules and platelet adhesion in sinusoids by 60%. In addition, Y-27632 decreased platelet aggregation in hepatic sinusoids and postsinusoidal venules by 69% and 81%. BDL caused a significant reduction of hepatic microvascular perfusion. Importantly, pretreatment with Y-27632 restored sinusoidal perfusion in cholestatic animals. Our findings demonstrate that Rho-kinase regulates multiple aspects of platelet interaction in the microcirculation of cholestatic animals. Moreover, inhibition of Rho-kinase signaling not only attenuates platelet responses but also maintains microvascular perfusion and protects against hepatocellular injury in cholestasis. Thus, targeting Rho-kinase signaling may be an effective way to protect against platelet-mediated liver injury in obstructive jaundice.
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| 7. |
- Lundblad, Cornelia, et al.
(författare)
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Effects of l-arginine on cerebral blood flow, microvascular permeability, number of perfused capillaries, and brain water content in the traumatized mouse brain.
- 2007
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Ingår i: Microvascular Research. - : Elsevier BV. - 1095-9319 .- 0026-2862. ; 74, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- It is has been suggested that decreased production of the vasodilatory and anti-aggregative substance NO (nitric oxide) may result in lower cerebral blood flow (CBF) in injured areas of the traumatized brain. The NO-precursor L-arginine has been shown to counteract CBF decreases early after trauma, but microcirculatory and more long-term effects on CBF of L-arginine have not been investigated. In an attempt to analyze effects Of L-arginine on the microcirculation in the traumatized brain, the present study was designed to evaluate the effects Of L-arginine compared to vehicle (0.9% saline) following a standardized controlled cortical-impact brain trauma in mice. Cerebral blood flow (autoradiography [C-14]-iodoantipyrine), number of perfused capillaries (FITC-dextran fluorescence technique), brain water content (wet vs. dry weight) and the blood to brain transfer constant K-i for [Cr-51]-EDTA were analyzed in the injured and the contralateral cortex. Cortical blood flow in the injured cortex was 0.43 +/- 0.3 mL/g/min and 0.8 +/- 0.3 mL/g/min 3 h after trauma in the vehicle and L-arginine groups, respectively (p < 0.05), and no treatment effect was seen 24 h after trauma. The number of perfused capillaries decreased following trauma and was unaffected by L-arginine. Ki increased following trauma and was unaffected by L-arginine. Brain water content was lower in the L-arginine group than in the vehicle group 3 h after trauma and there was no difference between the groups 24 h after trauma. We conclude that L-arginine reduces brain edema formation and improves cortical blood flow in the early phase after a brain trauma, whereas no circulatory effects can be seen after prolonged treatment.
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| 8. |
- Rousseau, Andreas, 1971-, et al.
(författare)
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Hyperoxia decreases cutaneous blood flow in high-perfusion areas
- 2007
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Ingår i: Microvascular Research. - : Elsevier BV. - 0026-2862 .- 1095-9319. ; 74:1, s. 15-22
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Tidskriftsartikel (refereegranskat)abstract
- The mechanism by which hyperoxia decreases blood flow is still not understood. Hyperoxemia-induced vasoconstriction is known to occur in many organs, including brain and retina, skeletal muscle, and myocardium. Whether this also occurs in skin is unknown.This study was conducted in healthy volunteers exposed intermittently to 100% oxygen (FIO2 1.0). Perfusion of forearm skin was measured by laser Doppler imaging (LDI). In series 1, it was measured in 7 subjects before, during, and after 15 min of oxygen breathing. In series 2, flow was measured, also during air and O2 breathing, after perfusion was raised by (a) sympathetic blockade (induced by a topically applied local anesthetic) (n = 9) and by (b) current-induced vasodilation (n = 8).In normal unperturbed skin, there was no significant change with hyperoxia. When basal perfusion was raised by topical anesthesia or by current, there was also no change in mean perfusion overall with hyperoxia. However, areas with the highest perfusion (upper decile) showed a significant perfusion decrement with hyperoxia (− 30% and − 20%, respectively; p < 0.001).Vasoconstriction with hyperoxia has been demonstrated in human skin. The fact that it is observed only when flow is increased above basal levels and then only in high-flow vessels suggests that cutaneous blood flow control is primarily regulated by variables other than oxygen.
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