Laser Doppler Flowmeter Research Articles

Blood flow modification attached to HIFU exposure mast cell degranulation

Introduction. One of the promising methods of treating oncological diseases is high-frequency focused ultrasound (HIFU). The high-frequency acoustic field generated by the emitters induces mechanothermal effects whose significance has not yet been fully assessed and their study will change the tactics of therapy. To analyze their role, we selected cellular perivascular regulators of local blood flow – mast cells (MCs). Changes in the microcirculation (MCT) allow us to judge the morphofunctional state of the MC. The aim of the study is to assess the state of the rat’s skin periphocal tissue blood flow and MCs morphofunctional properties after HIFU-exposure.Material and methods. Adult male Wistar rats were used. Animals were divided into 3 groups: control, non-contact local heating of the skin and HIFU-induced exposure. For HIFU, an experimental setting was used, consisting of a concave emitter H-148 S / N 010 with a central oscillation frequency of 1.4 MHz. In the averaged interference spot, the radiation intensity was 8.2 kW/cm2. The exposure duration from 150 to 700 ms. Depth of focus is about 1 mm. To assess the MCT, a laser doppler flowmeter was used. Material for the manufacture of film preparations of MCs was taken at the site of exposure and according to the standard method. MCs calculation was carried out using the software «Multimedia Catalog» taking into account their morphofunctional characteristics.Results. HIFU exposure led to a significant increase in blood flow in rat’s skin at an exposure time of 250 ms or more (p<0.01). The maximum increase in perfusion was noted at 400 ms. The highest increase in tissue blood flow with local heating was observed at 45°C (p<0.001). HIFU-exposure led to a significant decrease in the density of MCs in the subcutaneous fat tissue of rat’s skin compared with the control at an exposure time of 250 ms or more (p<0.05) and a significant decrease in the relative number of type I cells, and an increase in type II and III, which indicates degranulation (p<0.05). Similar changes in the amount and morphofunctional characteristics of MCs were observed in a series of experiments with local heating, but the changes were not so significant.Conclusions. With HIFU-induced exposure, increased MCT in the peripheral zones is observed, accompanied by processes of morphofunctional rearrangement of the MCs, which indicates a combined mechanothermal disturbance in the focus zone, which forms the spatiotemporal continuum of the thermal field.

Real-time optical vascular imaging: a method to assess the microvascular circulation of myofascial free flaps used in the head and neck region

Microvascular free flaps are considered the gold standard in head and neck reconstructive surgery. Myofascial flaps, in particular, are useful in certain oral and maxillofacial reconstruction cases, where mucosal regeneration over the transplanted tissue is planned. Despite high success rates, 1–6% of free flaps fail. A plethora of methods are available to assess transplanted tissue viability after reconstruction, including clinical observational monitoring, surface Doppler, implantable Doppler probe, colour Doppler sonography, laser Doppler flowmeter, surface temperature and indocyanine green angiography. However, no method has demonstrated adequate reliability or has proven to be cost-effective. The authors tested a technique called real-time optical vascular imaging to evaluate the microvascular circulation of myofascial free flaps. This technique was develop at Guy’s Hospital, London to observe the microvascular anatomy of the oral cavity in vivo, non-invasively and without the need for patient preparation, with the aim of detecting and monitoring oral diseases. This technology detects the red blood cells flowing inside the microvasculature at a depth of approximately 2mm, allowing the microvascular architecture and blood flow to be determined. This study showed that RTOVI may prove to be beneficial for the early detection of vascular compromise due to its immediacy and the feasibility of assessing multiple graft tissue regions.

The Effect of Shear Force on Skin Viability in Patients with Type 2 Diabetes.

Background Shear is a major risk factor in the development of diabetic foot ulcers, but its effect on the skin of patients with type 2 diabetes mellitus (DM) remains to be elucidated. The aim was to determine skin responses to shear in DM patients with and without diabetic polyneuropathy (DNP). Methods The forearm skin was loaded with 14.5 N shear (+2.4 kPa pressure) and with 3.5 kPa pressure for 30 minutes in 10 type 2 DM patients without DNP, 10 type 2 DM patients with DNP, and 10 healthy participants. A Sebutape collected IL-1α (measure of tissue damage). A laser Doppler flowmeter measured cutaneous blood cell flux (CBF) as a measure of the reactive hyperaemic skin response. Findings Reactive hyperaemia and IL-1α release was significantly increased after shear loading in all three groups and was higher compared to the responses to pressure loading. The reactive hyperaemic response after shear loading was impaired in patients with type 2 DM compared to healthy participants but did not differ between patients with and without DNP. The reactive hyperaemic response was negatively correlated with the blood glucose level but did not correlate with the DNP severity score. Interpretation Shear is important in the development of tissue damage, but the reparative responses to shear are impaired in patients with type 2 DM. DNP was not associated with altered skin responses, suggesting that the loss of protective sensation to sense shear to skin remains a key factor in the development of diabetic foot ulcers in patients with DNP.

Arterial Supercharging Is More Beneficial to Flap Survival Due to Quadruple Dilation of Venules

Background“Choke vessels” are communicating conduits between adjacent perforasomes in the skin. Most researches focus mainly on the arterial aspect of the “choke vessels” and neglect the venous aspect, an imbalance needed to be addressed. Materials and methodsThe study was divided into parts I, II, and III. Part I was for observation of the vascular morphological evolution in the choke zone after flap harvest in rats. Part II was for determination of the importance of the dilation of the arterial and venous components of “choke vessels” by preserving the iliolumbar artery (ILA group) or vein (ILV group). A laser Doppler flowmeter and a speckle flow imaging system were adopted for monitoring the hemodynamic impact caused by the different manipulation. Part III was for corroboration of part II by manipulation of other vessels. ResultsIn part I, the arteries and veins between the iliolumbar and intercostal perforasomes underwent modest dilation, whereas the venules between the veins nearly quadrupled in diameter. In part II, flaps in the ILA group were much more intensive in blood perfusion than flaps in the ILV group. The flap necrosis rate was 0.31 ± 0.07 in the ILV group, being significantly larger than 0.10 ± 0.03 in the ILA group. Part III confirmed that venous superdrainage is less efficacious in reducing flap necrosis than arterial supercharging, in which the position of the additional artery was far more important than the diameter. ConclusionsThe extensive dilation of the venous component of choke vessels makes a more potent compensatory role for venous drainage after flap harvest, indicating arterial supercharging is better in augmenting flap viability than venous superdrainage.

New cerebrovascular agent with hypotensive activity

Introduction: In cerebrovascular disorders, special attention is paid to a hypertensive cerebrovascular crisis, which combines a vascular injury of the brain and hypertension. The paper studies the cerebrovascular properties of the calcium channel blocker of S-Amlodipine nicotinate antihypertensive agent.
 Materials and methods: Tests were performed on 96 nonlinear male rats, measuring local blood flow in the cerebral cortex in 36 awake animals, using a laser Doppler flowmeter. Cerebral circulation was recorded in the animals when modeling ischemic and hemorrhagic brain injuries.
 Results and discussion: S-Amlodipine nicotinate (0.1 mg/kg i/v) shows a pronounced cerebrovascular activity in the models of ischemic and hemorrhagic injuries of the brain. In terms of the vasodilating effect in ischemic brain injury, the drug is comparable to mexidol, nimodipine, picamilon, but is superior to nimodipine and picamilon in terms of duration of action, and in the model of hemorrhagic stroke, S-Amlodipine nicotinate is superior to nimodipine and is comparable to picamilon and mexidol. The analysis of the mechanism of action of the agent revealed the participation of GABA A-receptors in the implementation of cerebrovascular properties of the agent.
 Conclusion: Significant cerebrovascular activity of S-Amlodipine nicotinate (0.1 mg/kg i/v) antihypertensive agent was revealed. The presence of GABAergic mechanism on cerebral blood flow in the agent action along with blockade of slow calcium channels ensures its high efficacy in treatment of both ischemic and hemorrhagic brain injuries

A new approach to the analysis of skin blood flow oscillations in human

It is considered that there are six non-overlapping frequency intervals with constant boundaries. These intervals correspond to different mechanisms of skin blood flow regulation. The boundaries do not depend on functional conditions but this statement should be verified. Also it remains unclear how the oscillatory components of skin blood flow are related. Thus the study is aimed to verify statistically the boundaries of frequency intervals, to test the hypothesis that the boundaries depend on age and to search for relationships between spectral components of skin blood flow. The study involved 105 healthy volunteers aged from 20 to 65 years, which were divided into two age groups. Skin blood flow was registered with laser Doppler flowmeter (LDF). Assessments of frequency interval boundaries and relationship between the frequency oscillatory components of blood flow were conducted with histogram approach, bootstrap method and correlation analysis. New frequency interval boundaries were found. They were different in two groups. A linear correlation and frequency areas with moderate (0.5–0.7) and high (>0.7) correlation coefficients were found between spectral components of blood flow. The dependence of these correlations on the age was shown. Thus we proposed a conceptually new approach to analysis of spectral components of skin microhemodynamics and interpretation of results obtained by laser Doppler techniques. This approach is the result of the development of modern understanding of relationships between skin blood flow regulation mechanisms and spectral components of LDF signals. It allows one to have a new look at these relationships as well as demonstrates their dependence on the functional state of the organism as a whole.

Hemodynamic changes in hepatic sinusoids of hepatic steatosis mice.

BACKGROUNDFatty liver (FL) is now a worldwide disease. For decades, researchers have been kept trying to elucidate the mechanism of FL at the molecular level, but rarely involve the study of morphology and medical physics. Traditionally, it was believed that hemodynamic changes occur only when fibrosis occurs, but it has been proved that these changes already show in steatosis stage, which may help to reveal the pathogenesis and its progress. Because the pseudolobules are not formed during the steatosis stage, this phenomenon may be caused by the compression of the liver microcirculation and changes in the hemodynamics.AIMTo understand the pathogenesis of hepatic steatosis and to study the hemodynamic changes associated with hepatic steatosis.METHODSEight-week-old male C57BL/6 mice were divided into three groups randomly (control group, 2-wk group, and 4-wk group), with 16 mice per group. A hepatic steatosis model was established by subcutaneous injection of carbon tetrachloride in mice. After establishing the model, liver tissue from mice was stained with hematoxylin and eosin (HE), and oil red O stains. Blood was collected from the angular vein, and hemorheological parameters were estimated. A two-photon fluorescence microscope was used to examine the flow properties of red blood cells in the hepatic sinusoids.RESULTSOil red O staining indicated lipid accumulation in the liver after CCl4 treatment. HE staining indicated narrowing of the hepatic sinusoidal vessels. No significant difference was observed between the 2-wk and 4-wk groups of mice on morphological examination. Hemorheological tests included whole blood viscosity (mPas, γ = 10 s-1/γ = 100 s-1) (8.83 ± 2.22/4.69 ± 1.16, 7.73 ± 2.46/4.22 ± 1.32, and 8.06 ± 2.88/4.22 ± 1.50), red blood cell volume (%) (51.00 ± 4.00, 42.00 ± 5.00, and 40.00 ± 3.00), the content of plasma fibrinase (g/L) (3.80 ± 0.50, 2.90 ± 0.80, and 2.30 ± 0.70), erythrocyte deformation index (%) (44.49 ± 5.81, 48.00 ± 15.29, and 44.36 ± 15.01), erythrocyte electrophoresis rate (mm/s per V/m) (0.55 ± 0.11, 0.50 ± 0.11, and 0.60 ± 0.20), revealing pathological changes in plasma components and red blood cells of hepatic steatosis. Assessment of blood flow velocity in the hepatic sinusoids with a laser Doppler flowmeter (mL/min per 100 g) (94.43 ± 14.64, 80.00 ± 12.12, and 67.26 ± 5.92) and two-photon laser scanning microscope (μm/s) (325.68 ± 112.66, 213.53 ± 65.33, and 173.26 ± 44.02) revealed that as the modeling time increased, the blood flow velocity in the hepatic sinusoids decreased gradually, and the diameter of the hepatic sinusoids became smaller (μm) (10.28 ± 1.40, 6.84 ± 0.93, and 5.82 ± 0.79).CONCLUSIONThe inner diameter of the hepatic sinusoids decreases along with the decrease in the blood flow velocity within the sinusoids and the changes in the systemic hemorheology.

Neuro-protective effect of monomethyl fumarate on ischemia reperfusion injury in rats: Role of Nrf2/HO1 pathway in peri-infarct region

Post stroke recanalization has been associated with increased risk of oxidative stress. Stimulating endogenous antioxidant pathway by activation of nuclear factor erythroid-2-related factor-2 (Nrf2) plays a key role in neuronal defense against inflammation and oxidative stress in penumbra. Here, we explored whether monomethyl fumarate (MMF) could produce neuro-protection after ischemia/reperfusion (I/R) injury via Nrf2/HO1 activation. In male SD rats, middle cerebral artery was occluded for 90 min and confirmed using Laser Doppler flowmeter. MMF (10, 20 and 40 mg/kg) was administered in two divided doses at 30 min post ischemia and 5–10 min after reperfusion. After 24 h, effect on neurobehavioral parameters, infarct damage by TTC staining and MRI, oxidative stress and inflammatory cytokines were assessed. Expression studies of nuclear Nrf2 and cytoplasmic HO1 were performed in peri-infarct cortex and striatum; followed by dual immunofluorescence study to check the specific cell type. I/R induced neurobehavioral deficits and infarct damage were significantly (p < 0.05) attenuated by MMF (20 and 40 mg/kg). MMF, 20 mg/kg, significantly normalized I/R induced altered redox status and increased levels of TNF-α, IL-1β in the ipsilateral cortex. MRI data showed significantly reduced infarct in cortex but not in striatum after MMF treatment. Expression of nuclear Nrf2 and cytoplasmic HO1 were significantly (p < 0.05) increased in peri-infarct cortex after treatment with MMF. Additionally, dual immunofluorescence showed increased Nrf2 expression in neurons and HO1 expression in neurons as well as astrocytes in peri-infarct cortex after MMF treatment. Our results show the neuro-protective potential of MMF probably by restricting the progression of damage from striatum to cortex through activation of Nrf2/HO1 pathway in peri-infarct cortex.

Assessment of Skin Blood Flow Following Acute Intravenous Alcohol, and Association with Subjective Perceptions, in Social Drinkers.

The objective of this study was to determine the effect of acute intravenous (IV) alcohol infusion on skin blood flow (SBF) response, measured at fingertip and earlobe, and subjective responses associated with SBF in social drinkers. Twenty-four social drinkers underwent a computer-assisted alcohol self-infusion study. SBF was measured continuously using laser Doppler flow meter, with the probe placed on the fingertip or earlobe. Perfusion recordings were collected at baseline, and at 0-minute (0 to 5minutes), 10-minute (10 to 15minutes), and 20-minute (20 to 25minutes) time points during the priming phase of IV alcohol self-administration paradigm at low breath alcohol levels of approximately 30mg%. Subjective response was measured using the Drug Effects Questionnaire (DEQ) and Biphasic Alcohol Effects Scale. Overall SBF (collective data from both fingertip and earlobe) and SBF by each site showed significant drop at 0minutes and then subsequent significant elevation with alcohol self-administration. Males showed higher overall SBF at baseline and 0minutes than the females. At fingertip site, lowering in 0-minute SBF compared to baseline, and subsequent significant increase at the 10- and 20-minute SBF recordings were observed. DEQ measures of "like" and "want more" alcohol were significantly associated with 10- and 20-minute SBF recordings collected at fingertip site. The changes in SBF following acute IV alcohol exposure are consistent with the sympathetic response of alcohol on the cardiovascular system. This acute hemodynamic effect characterizes differences in blood flow that are sensitive to relatively low levels of acute alcohol exposure. The association of subjective perceptions with the SBF response provides evidence of the psychophysiological effects of alcohol at low levels of exposure.

Impaired functional recovery of endothelial colony-forming cells from moyamoya disease in a chronic cerebral hypoperfusion rat model.

OBJECTIVEEndothelial colony-forming cells (ECFCs) isolated from pediatric patients with moyamoya disease (MMD) have demonstrated decreased numbers and defective functioning in in vitro experiments. However, the function of ECFCs has not been evaluated using in vivo animal models. In this study, the authors compared normal and MMD ECFCs using a chronic cerebral hypoperfusion (CCH) rat model.METHODSA CCH rat model was made via ligation of the bilateral common carotid arteries (2-vessel occlusion [2-VO]). The rats were divided into three experimental groups: vehicle-treated (n = 8), normal ECFC-treated (n = 8), and MMD ECFC-treated (n = 8). ECFCs were injected into the cisterna magna. A laser Doppler flowmeter was used to evaluate cerebral blood flow, and a radial arm maze test was used to examine cognitive function. Neuropathological examinations of the hippocampus and agranular cortex were performed using hematoxylin and eosin and Luxol fast blue staining in addition to immunofluorescence with CD31, von Willebrand factor, NeuN, myelin basic protein, glial fibrillary acidic protein, and cleaved caspase-3 antibodies.RESULTSThe normal ECFC-treated group exhibited improvement in the restoration of cerebral perfusion and in behavior compared with the vehicle-treated and MMD ECFC-treated groups at the 12-week follow-up after the 2-VO surgery. The normal ECFC-treated group showed a greater amount of neovasculogenesis and neurogenesis, with less apoptosis, than the other groups.CONCLUSIONSThese results support the impaired functional recovery of MMD ECFCs compared with normal ECFCs in a CCH rat model. This in vivo study suggests the functional role of ECFCs in the pathogenesis of MMD.

Retigabine protects the blood-brain barrier by regulating tight junctions between cerebral vascular endothelial cells in cerebral ischemia-reperfusion rats.

To investigate the effect of retigabine on the blood-brain barrier permeability in rats with cerebral ischemia-reperfusion and its mechanism. A total of 90 Sprague-Dawley (SD) rats were selected to prepare a rat model of focal cerebral ischemia-reperfusion. The blood flow changes were detected using a laser Doppler flow meter, the percentage of the cerebral infarction volume was measured by means of the triphenyl tetrazolium chloride (TTC) staining, the effect of retigabine on the permeability of the blood-brain barrier after cerebral ischemia-reperfusion was examined via Evans blue (EB) staining, and the state of tight junctions between endothelial cells was determined via the transmission electron microscopy (TEM) technique. Immunohistochemistry was used to detect the effects of retigabine on the distribution and expressions of tight junction-associated proteins in the cerebral ischemia-reperfusion blood-brain barrier. Western blotting was adopted to examine the changes in the expressions of related proteins in cerebral ischemia-reperfusion tissues. At 48 h and 96 h after cerebral ischemia-reperfusion, retigabine notably reduced the cerebral infarction volume of rats, and the tight junctions between microvascular endothelial cells in the ischemic area opened up, the permeability of the blood-brain barrier was remarkably increased, and the permeability of the blood-brain barrier was significantly reduced under the action of retigabine. The expressions of claudin-5, occludin, and ZO-1 in the blood-brain barrier of the ischemic brain tissue significantly declined, and retigabine notably increased the expressions of three proteins and their distributions along the microvessels. At 3 h, 24 h, 48 h, and 96 h after cerebral ischemia-reperfusion, the expressions of the MMP-2 protein and MMP-9 protein in the ischemic brain tissue were evidently increased, which were inhibited by retigabine. Moreover, the expressions of the PKCδ protein in the ischemic brain tissue were markedly increased, which were significantly inhibited by retigabine. The regulatory roles of retigabine in the distribution and expressions of claudin-5, occludin, and ZO-1 may be associated with the inhibition of the expressions of the MMP-2, MMP-9, and PKCδ proteins.

PO-087 4-weeks hypoxia (HHL) training improves rowers’ cutaneous microcirculation

Objective Sport scientists always pay attention to cardiorespiratory and hematologic system on benefit of hypoxic training, but peripheral circulation may be one of these benefit, which is one cause of improving performance. So, in order to know whether or not hypoxic training affect athletes’ cutaneous microcirculation, we test rowers’ microcirculation for 4 weeks’ High Live-High Train-Low exercise(HHL).&#x0D; Methods The subject is 21 male rowers of Shanghai rowing team.12 of them take part in 4 weeks HHL (train and live at 2500m, exercise at 100m), while 9 of them train in normoxia. Forearm and leg cutaneous blood flow(CBF) was measured using a laser doppler flowmeter (PeriFlux600, Perimed, Sweden) at room temperature (22℃) with subject lying position and after testing in that position for at least 10min. We tested the forearm and leg blood flow, and also the blood flow when localized heating to 44℃ for 3 mins. Microvascular reactivity(MVR) was evaluated form the maximal post occlusive reactive hyperemia(PORH) following 3-min forearm ischemia produced by cuff inflation (200mm Hg). Similar procedures have been used by other investigators. Blood pressure was measured by brachial auscultation. SPO2 and heart rate was measured by a hand hold pulse oximeter (NONIN, 9500, USA) .The blood flow was measured 4 times, baseline, 1stweek, 3rdweek and post.&#x0D; Results Blood flow and CMBC of forearm of HHL increased significantly at 1stweek(8.9,13.0;112.0,151.0,P&lt;0.05), but thigh and NOM group did not increase. The lowest and highest blood flow of PORH both increase at 1stweek(2,9,3.2;46.0,53.0;0.05&lt;P&lt;0.1). At 3rdweek, HHL group’s resting blood flow and CMBC of forearm is lower than 1stweek(9.3,13.0;124.5,151.0), but higher than pretraining, but velocity of blood flow decreased(8.2,9.2). &#x0D; These results suggest at early stage of HHL, vasoconstriction may be dominant. But when rowers suffer more and more hypoxia, vasodilation and angiogenesis may play a key role in their skin blood flow. At 3rdweek after training, the blood flow and CMBC are similar with baseline.&#x0D; Conclusions 4 weeks HHL training of rowers increase forearm blood flow, but no thigh. This is because thigh is main working muscle of rowers, which may be affected by training status and fatigue. And also, PORH reserve capacity is an indicator of endothelial function. In this study, we find HHL rowers increase their PORH reserve capacity, which means endothelial function is improved by hypoxia training. So, besides the traditional research of Hematologic System on hypoxia training, we find 4 weeks HHL training increase forearm blood flow and improve endothelial function. This may be one mechanism of improving performance, which need more studies to confirm.

The Skin Bridge Is More Important as an Additional Venous Draining Route in a Perforator-Plus Flap

BackgroundThe skin bridge in the perforator-plus flap is considered as an additional source for arterial input and venous drainage apart from the perforator. However, its exact role requires further elucidation. Materials and methodsForty rats that underwent flap elevation with a size of 9 × 3 cm on the dorsum were evenly divided into a perforators-intact group with an intact vascular pedicle, an artery-deficient group with the artery ligated, a vein-deficient group with the vein ligated, and a perforators-deficient group with both vessels ligated. The blood perfusion was measured using a laser Doppler flowmeter. On the seventh day, the necrosis rate of the flaps was calculated and the diameter of vessels in the skin bridge was measured. ResultsThe perfusion pattern was similar between the perforators-intact group and vein-deficient group, as well as between the perforators-deficient group and artery-deficient group. The blood perfusion was much more robust in the perforators-intact and vein-deficient groups. The necrosis rate in the perforators-deficient group (26 ± 1%) was not significantly different from that in the artery-deficient group (29 ± 1%), both of which was significantly larger than that in the perforator-intact (11 ± 3%) and vein-deficient groups (12 ± 4%) (P ˂ 0.001). The venous network of the skin base in the vein-deficient and perforators-deficient groups dilated dramatically, whereas the arterial network in the artery-deficient and perforators-deficient groups had a very modest expansion. ConclusionsThe skin base in a perforator-plus flap is much more important as an additional route for vein drainage than for arterial input.

Monitoring tumor progression by mapping skin microcirculation with laser Doppler flowmetry.

Laser Doppler flow meter is a safe, useful, and noninvasive tool to monitor microvascular blood flow. It measures the changes in flow either over time or differences in flow over an area of skin or other exposed tissue. The primary function of LDF is to produce blood perfusion output signal that is proportional to the red blood cell perfusion (or flux). A simple analog-based laser Doppler flow meter is used to record the biosignals arising from the microvascular network of a surface lesion in the face of a human being. An innovative technique is developed to overcome one of the major technical limitations that involved removing the continuous artifacts or noise generated by the movement of the cable, the probe as well as the operator or the patient. A color heat map in MATLAB is created to facilitate its easy analysis, interpretation, and understanding of the blood flow changes over a period of time across a cross-sectional area in an image format processed after acquiring the biosignals (flux) using LDF by the clinicians or by the technician who is performing the vascular assessment of the lesion.

Assessment of Plasma Coagulation on Liver Tissue in a Large Animal Model In Vivo.

Plasma coagulation as a form of electrocautery is used in liver surgery for decades to seal the large liver cut surface after major hepatectomy to prevent hemorrhages at a later stage. The exact effects of plasma coagulation on liver tissue are only poorly examined. In our porcine model, the coagulation effects can be examined close to the clinical application. A combined laser Doppler flowmeter and spectrophotometer documents microcirculation changes during coagulation at 8 mm tissue depth noninvasively, providing quantifiable information about hemostasis beyond the subjective clinical impression. The temperature at coagulation site is assessed with an infrared thermometer prior and post coagulation and with a thermographic camera during coagulation, a measurement of the gas beam temperature is not possible due to the upper threshold of the devices. The depth of coagulation is measured microscopically on hematoxylin/eosin stained sections after calibration with an object micrometer and gives an exact information about the power setting-coagulation depth-relation. The sealing effect is examined on the bile ducts as it is not possible for a plasma coagulator to seal larger blood vessels. Burst pressure experiments are carried out on explanted organs to rule out blood pressure related effects.

The response of peripheral microcirculation to gravity-induced changes

BackgroundThe peripheral microcirculation supplies fresh blood to the small blood vessels, providing oxygen and nutrients to the tissues, removing waste, and maintaining normal homeostatic conditions. The goal of this study was to characterize the response of the peripheral microcirculation, in terms of blood flow and tissue oxygenation variables, to gravity-induced changes. MethodsThe study included 20 healthy volunteers and the experiment involved monitoring central and peripheral variables with the right hand positioned at different heights. These positions correspond to various gravitational levels. Peripheral perfusion and oxygenation were monitored using a laser Doppler flowmeter, photoplethysmograph, and transcutaneous oxygen tension monitor. Local blood pressure and respiration rate were also measured. FindingsAt the heart level, tissue oxygenation displayed a nadir, while capillary flow displayed a peak. Similar but weaker changes were observed at the control hand. In contrast, the photoplethysmograph's amplitude strongly decreased upon reducing the arm position below heart level. Both systolic and diastolic pressures decreased linearly between the highest to lowest arm position. InterpretationThe results may reflect peripheral compensation mechanisms, as well as an interaction between the central and peripheral cardiovascular systems, in response to local changes in blood pressure. The observed dependence of the oxygenation pattern on height could lead to important new insights for the diagnosis and treatment of problems in the regulation of tissue perfusion.

Peripheral Resistance Baroreflex During Incremental Bicycle Ergometer Exercise: Characterization and Correlation With Cardiac Baroreflex.

The arm of the baroreflex (BR) controlling peripheral resistances (PR), labeled as BR of PR (prBR), was characterized through an extension of the cardiac BR (cBR) sequence analysis. The method exploits recordings of skin blood flow (SBF) from the palm of the non-dominant hand via a laser Doppler flowmeter and of arterial pressure (AP) from the middle finger of the same hand via a plethysmographic device. PR was estimated beat-by-beat as the ratio of mean AP to mean SBF computed over the same heart period (HP). Peripheral resistances-diastolic arterial pressure (PR-DAP) sequences featuring simultaneous increases of PR and decreases of diastolic AP (DAP) or vice versa were identified and the slope of the regression line in the (DAP, PR) plane was taken as an estimate of prBR sensitivity (BRSprBR). The percentage of prBR sequences (SEQ%prBR) was taken as a measure of prBR involvement and the prBR effectiveness index (EIprBR) was computed as the fraction of DAP sequences capable to drive antiparallel PR variations. Analogous markers were computed over cBR from HP and systolic AP (SAP) variability [i.e., cBR sensitivity (BRScBR), percentage of cBR sequences (SEQ%cBR), and effectiveness index of the cBR (EIcBR)]. prBR and cBR were typified during incremental light-to-moderate bicycle ergometer exercise at 10, 20, and 30% of the maximum effort in 16 healthy subjects (aged from 22 to 58 years, six males). We found that: (i) BRScBR decreased gradually with the challenge, while BRSprBR declined only at the heaviest workload; (ii) SEQ%cBR decreased solely at the lightest workload, while the decline of SEQ%prBR was significant regardless of the intensity of the challenge; (iii) EIprBR and EIcBR were not affected by exercise; (iv) after pooling together all the data regardless of the experimental conditions, BRSprBR and BRScBR were uncorrelated, while SEQ%cBR and SEQ%prBR as well as EIcBR and EIprBR, were significantly and positively correlated; (v) when the correlation between SEQ%cBR and SEQ%prBR and between EIcBR and EIprBR was assessed separately in each experimental condition, it was not systematically detected. This study suggests that prBR characterization provides information complementary to cBR that might be fruitfully exploited to improve patients’ risk stratification.

Effects of Morroniside on the Viability of Random Skin Flaps in Rats

ABSTRACTObjective: The purpose of our experiment was to determine whether morroniside can improve the survival of ischemic skin flaps in rats. Methodology: A total of 40 male Sprague-Dawley rats were randomly divided into two groups (control group and treatment group). Modified McFarlane flaps were performed (causally based, 9 cm × 3 cm). The percentage of survival of each flap was calculated. Flap blood flows were measured by Laser-Doppler flowmeter. Flap vasculature was assessed by angiography after Lead oxide-gelatin injection. Vascular endothelial growth factor (VEGF) was evaluated by immunochemistry. Superoxide Dismutase (SOD) level and malondiadehyde (MDA) content were determined using assay kits. Results: At the seventh postoperative day, the morroniside-treated rats showed a higher percentage of flap survival than the control rats. Flap perfusion and the level of vascular endothelial growth factor were significantly elevated in the morroniside-treated group. In the treatment group, the distal section of the flap was nearly saturated with contrast agent, while in the control group, the contrast agent perfused only half of the flap. In the treatment group, morroniside administration significantly increased SOD level and reduced MDA content. Conclusion: Morroniside can enhance ischemic flap survival.

Betulinic acid, a natural PDE inhibitor restores hippocampal cAMP/cGMP and BDNF, improve cerebral blood flow and recover memory deficits in permanent BCCAO induced vascular dementia in rats

Vascular dementia (VaD) is the second most common form of senile dementia, embraces memory deficits, neuroinflammation, executive function damage, mood and behavioral changes and abnormal cerebral blood flow. The purpose of the study was to explore the therapeutic potential of betulinic acid in bilateral common carotid artery occlusion (BCCAO) induced VaD in experimental rats. VaD was induced by BCCAO in rats and betulinic acid (10 and 15 mg/kg/day po) was administered 1 week after surgery. The cerebral blood pressure of the animal was recorded before and after the treatment using Laser Doppler flow meter. Object recognition task for non-spatial, Morris water maze for spatial and locomotor activity was performed to evaluate behavioral changes in rats. At the end of the study, animals were decapitated and hippocampus was separated to perform biochemical, neuroinflammatory and second messengers cAMP/cGMP analysis. Histology was done to study the brain pathophysiology. BCCAO surgery was able to significantly impaired memory in rats as observed behavioral and biochemical parameters. Moreover, BA demonstrated a neuroprotective effect in a dose-dependent manner. BA was able to re-establish cerebral blood flow, restore behavioral parameters and showed significant improvements in the as cAMP,cGMP and BDNF levels, restrain the oxidative stress and inflammatory parameters. In histopathology, betulinic acid treated groups showed a decrease in microgliosis and less pathological abnormalities comparable to diseased rat's brain. The observed effect might be attributed to the neuroprotective potential of betulinic acid and its ability to restore cognitive impairment and hippocampal neurochemistry in VaD.

Estimated thermal sensation models by physiological parameters during wind chill stimulation in the indoor environment

Thermal sensation is the occupants’ response about the thermal variation of any given environment. Data regarding thermal sensation can be collected to enhance an air conditioner's capabilities to improve the thermal environment of an area. In this study, six physiological parameters, including skin blood flow (SBF), skin temperatures (forehead, arm, and hands) sweat areas and sweat pore diameters of the body were monitored during a two-step wind chill stimulation in an indoor environment. These physiological parameters were measured by a laser Doppler flowmeter, three surface thermometers, and a digital universal serial bus (USB) microscope. The sample group consisted of 12 undergraduate students who were recruited to be test subjects. The correlation coefficients between the aforementioned six physiological parameters and the Thermal Sensation Vote (TSV) were then analyzed. These physiological parameters were used to develop eight estimated TSV models. Of all the parameters measured for the TSV models, skin temperatures of the forehead and arms as well as SBF measurements provided the most accurate results. In contrast, sweat area measurements had the lowest accuracy under the experimental conditions of this study. Therefore, the estimated TSV models based on the skin temperature measured at the forehead or the combined physiological parameters would provide the most timely thermal comfort response of the occupants and facilitate the better intelligent control of an air-conditioning system for an indoor environment.