Laser Doppler Perfusion Research Articles

Contrasting roles of E2F2 and E2F3 in endothelial cell growth and ischemic angiogenesis

The growth of new blood vessels after ischemic injury requires endothelial cells (ECs) to divide and proliferate, and the E2F transcription factors are key regulators of the genes responsible for cell-cycle progression; however, the specific roles of individual E2Fs in ECs are largely unknown. To determine the roles of E2F2 and E2F3 in EC proliferation and the angiogenic response to ischemic injury, hind–limb ischemia was surgically induced in E2F2−/− mice, endothelial-specific E2F3-knockout (EndoE2F3∆/∆) mice, and their littermates with wild-type E2F2 and E2F3 expression. Two weeks later, Laser-Doppler perfusion measurements, capillary density, and endothelial proliferation were significantly greater in E2F2−/− mice and significantly lower in EndoE2F3∆/∆ mice than in their littermates, and EndoE2F3∆/∆ mice also developed toe and limb necrosis. The loss of E2F2 expression was associated with increases in the proliferation and G1/S-phase gene expression of isolated ECs, while the loss of E2F3 expression led to declines in these parameters. Thus E2F2 impairs, and endothelial E2F3 promotes, the angiogenic response to peripheral ischemic injury through corresponding changes in EC cell-cycle progression.

Role of Endothelial Soluble Epoxide Hydrolase in Cerebrovascular Function and Ischemic Injury

Soluble Epoxide Hydrolase (sEH) is a key enzyme in the metabolism and termination of action of epoxyeicosatrienoic acids, derivatives of arachidonic acid, which are protective against ischemic stroke. Mice lacking sEH globally are protected from injury following stroke; however, little is known about the role of endothelial sEH in brain ischemia. We generated transgenic mice with endothelial-specific expression of human sEH (Tie2-hsEH), and assessed the effect of transgenic overexpression of endothelial sEH on endothelium-dependent vascular reactivity and ischemic injury following middle cerebral artery occlusion (MCAO). Compared to wild-type, male Tie2-hsEH mice exhibited impaired vasodilation in response to stimulation with 1 µM acetylcholine as assessed by laser-Doppler perfusion monitoring in an in-vivo cranial window preparation. No difference in infarct size was observed between wild-type and Tie2-hsEH male mice. In females, however, Tie2-hsEH mice sustained larger infarcts in striatum, but not cortex, compared to wild-type mice. Sex difference in ischemic injury was maintained in the cortex of Tie2-hsEH mice. In the striatum, expression of Tie2-hsEH resulted in a sex difference, with larger infarct in females than males. These findings demonstrate that transgenic expression of sEH in endothelium results in impaired endothelium-dependent vasodilation in the cerebral circulation, and that females are more susceptible to enhanced ischemic damage as a result of increased endothelial sEH than males, especially in end-arteriolar striatal region.

Skin microvascular morphology and hemodynamics during treatment with veno-arterial extra-corporeal membrane oxygenation

To explore the potentials of microcirculatory assessments for predicting outcome of patients treated with extra corporeal membrane oxygenation for cardiogenic shock. Eight patients with acute cardiogenic shock treated with ECMO and eight healthy controls were examined with skin vital microscopy and laser Doppler perfusion measurements. Three patients died on ECMO (group 1). Five patients were successfully weaned off ECMO (group 2). Four patients were discharged from hospital and one died after successful weaning from bleeding complications. Patients surviving ECMO (group 2) had microcirculatory findings comparable with healthy controls. Patients in group 1 showed major skin microvascular pathology: pericapillary bleedings (n = 1), pericapillary dark haloes (n = 2) and capillary micro thrombi (n = 1). As compared with survivors they had lower functional capillary density (FCD) (n = 3), higher heterogeneity of functional capillary density (n = 3) and significantly reduced capillary mean flow-categorical velocity (n = 2). Laser Doppler measurements in group 1 had non-significant lower laser Doppler flux values as compared with survivors and controls. Skin microvascular pathology as detected with video microscopy (pericapillary bleedings or haloes, micro-thrombi/capillaries with "no flow", low FCD with high spatial distribution heterogeneity or low mean flow-categorial velocity) seems to be associated with poor prognosis.

QiShenYiQi Pills, a Compound Chinese Medicine, Ameliorates Doxorubicin-Induced Myocardial Structure Damage and Cardiac Dysfunction in Rats

QiShenYiQi Pills (QSYQ) is a compound Chinese medicine used for treatment of cardiovascular diseases. The present study investigated the effects of QSYQ on the Doxorubicin- (DOX-) induced disorders in rat cardiac structure and function and the possible mechanism underlying. A total of 24 male Sprague-Dawley rats were administrated by intraperitoneal injections with DOX at a dose of 2.5 mg/kg, once every day for a total of 6 times. After the 6th injection, the rats were evaluated by echocardiographic analysis, and the animals with injured heart (n = 14) were divided into 2 groups and further treated with (n = 7) or without (n = 7) QSYQ by gavage at a dose of 0.2 g/day, once a day, over the next 2 weeks. Two weeks after QSYQ treatment, the following variables were assessed: myocardial blood flow (MBF) by Laser-Doppler Perfusion Imager, the ratio of heart weight to body weight (HW/BW), myocardial histology, myocardial content of ATP, AMP, free fatty acids (FFAs) and AMP/ATP by ELISA, and expression of PPARα, PGC-1α, and ATP 5D by Western blot. Statistical analysis was performed using one-way ANOVA followed by Turkey test for multiple comparisons. DOX challenge significantly increased left ventricular internal diameter and HW/BW and decreased the thickness of the left ventricular posterior wall, the left ventricle ejection fraction, and the left ventricle fractional shortening. DOX also increased AMP, FFA, and AMP/ATP, decreased ATP, and downregulated the protein content of ATP 5D, PPAR α, and PGC-1 α. All these DOX-induced cardiac insults were attenuated significantly by QSYQ treatment. These results show the potential of QSYQ to ameliorate DOX-induced disorders in cardiac structure and function; this effect may be related to the increase in myocardial ATP content via the upregulation of ATP 5D, PPAR α, and PGC-1 α and the oxidation of FFA.

Healing process of venous ulcers: the role of microcirculation

In order to describe adequately the process of healing in the intermediate degrees, we investigated microcirculatory changes in the venous ulcers at well-defined stages of wound repair. We investigated dynamic changes in microcirculation during the healing process of venous ulcers. Ten venous ulcers were investigated in three consecutive clinical stages of wound healing: non granulation tissue (NGTA), GTA and scar. Subpapillary microcirculation was measured by laser Doppler perfusion (LDP) imaging and expressed using LDP values in arbitrary units. Nutritive perfusion by capillary microscopy and expressed as capillary density (CD) - the number of capillaries per square millimetre. Before the development of GTA the LDP was low (median 1·35; lower-upper quartiles 0·71-1·83) accompanied with zero CD in all but one patient who had a density of 1. With the first appearance of GTA in the same area, the LDP was improved (2·22; 1·12-2·33; P = 0·0024) when compared with NGTA, in combination with a significant increase in CD (1·75; 0-3; P = 0·0054). In scar, the LDP was similar to that in the NGTA (1·03; 0·77-1·83; P = 0·278), combined with the highest CD (5·75; 4·5-8) in comparison with the previous stages of the area (for both pairs, P < 0·0001). Venous ulcers are caused by poor nutritive and subpapillary perfusion. Subpapillary perfusion plays a major role in the formation of GTA. In a scar, the increased nutritive perfusion is sufficient to cover the blood supply and keep skin viable while subpapillary perfusion is low.

Abstract 27: Antioxidant Carbon-based Nanomaterials: In-vitro Protection and In- vivo Effects on the Neurovascular Unit

Introduction: Dysfunction of the cerebrovasculature, manifested by poor reperfusion and loss of autoregulation, is a feature of ischemia and traumatic brain injury (TBI). Oxidative stress is implicated in this effect. Conventional antioxidants have not proven clinically effective. Nanomaterials are an emerging class of antioxidants with potential advantages including quenching of oxidative radicals without need for enzymatic transformation. Objectives: We tested whether the carbon nanomaterials, poly(ethylene gylcol)-functionalized hydrophilic carbon clusters (PEG-HCCs) are antioxidants and determined their effect on the cerebrovasculature following mild experimental TBI and hypotension. Methods: HCCs were generated by treating single wall carbon nanotubes with oleum and nitric acid. HCCs were functionalized with PEG via coupling to carboxcylic acids. The ability to quench superoxide anion (SO) was determined in solution and b.End3 cultured brain endothelial cells after administering the electron chain transport inhibitor Antimycin A (AntA) using dihydroethidium (DHE) fluorescence flow cytometry. In-vivo studies were performed in Long Evans rats following mild TBI (3m/s; 2.5 mm deformation; 80 ms duration) and 50 mins. hemorrhagic hypotension followed by resuscitation with Lactated Ringers ( Figure : Resus ) then by shed blood ( Hospital ). Treatment with 2 mg/kg PEG-HCCs in 1 mL or PBS was initiated prior to the “Hospital” phase. Laser Doppler perfusion (LDF) was measured to 6 hours post-TBI. Results: DHE fluorescence induced by AntA was eliminated by post-treatment with PEG-HCCs (2-4 mg/L; 15 min post-AntA). At that concentration, there was no innate toxicity in cells determined by clonogenic and trypan blue assay. Only pre-treatment with a 10X excess of SO dismutase (SOD) achieved comparable DHE effect. PEG-HCC post-treatment improved cell survival after a higher dose of AntA, to 65% of baseline compared to 23% for SOD. In-vivo following TBI, hypotension reduced relative LDF to approximately 30% ( Fig ). Administered just prior to shed blood nanotubes restored LDF to 100% of baseline while the vehicle group remained significantly lower at 56%. LDF declined in all groups over time. Conclusions: PEG-HCCs are biocompatible with b.End3 cells and rapidly protected these cells from oxidative stress. PEG-HCCs at a clinically realistic time point improved cerebrovasculature dysfunction post-TBI/hypotension. The duration of effect is consistent with blood half life after a single dose. Longer term dosing studies are underway to establish the effect on outcome and reperfusion injury.

Attenuating effect of post-treatment with QiShen YiQi Pills on myocardial fibrosis in rat cardiac hypertrophy

QiShen YiQi Pills(®) (QSYQ) is a compound Chinese medicine used for treatment of cardiovascular diseases. However, the potential of QSYQ to inhibit cardiac fibrosis in left ventricle hypertrophy is not explored to date. We investigated the effects of post-treatment with QSYQ on rat myocardial fibrosis in left ventricle hypertrophy induced by pressure over-load through ascending aortic stenosis. QSYQ was administrated 4 weeks after the surgery, at a dose of 0.8 g/kg/day over the next 4 weeks, while echocardiography was performed 4 and 8 weeks, respectively, after the surgery. Eight weeks after the surgery, myocardial blood flow was determined by Laser-Doppler Perfusion Imager and the ratio of heart weight to body weight (HW/BW) was estimated, in concurrent evaluation of myocardial histology and ultrastructure, as well as collagen content by sirius red staining, and immunohistochemistry staining for CD68 and transforming growth factor beta 1. Post-treatment with QSYQ significantly alleviated left ventricular posterior wall end diastolic thickness and the HW/BW, increased left ventricle ejection fraction and left ventricle fractional shortening. QSYQ also decreased myocardial fibrosis size. The expression of CD68 and transforming growth factor beta 1 were obviously suppressed after QSYQ treatment. The results suggest that post-treatment with QSYQ attenuates pressure over-load-induced cardiac hypertrophy and myocardial fibrosis through interfering in inflammatory process.

Central and Peripheral Fatigue during Passive and Exercise-Induced Hyperthermia

Hyperthermia was induced during prolonged exercise (ExH) and passive heating (PaH) to isolate the influence of exercise on neuromuscular function during a maximal voluntary isometric contraction (MVC) of the quadriceps under heat stress. The influence of cardiovascular strain in limiting endurance performance in the heat was also examined. On separate days, eight males cycled to exhaustion at 60% maximal oxygen uptake or were immersed in a water bath (∼41°C) until rectal temperature (Tre) increased to 39.5°C. The ExH and PaH interventions were performed in ambient conditions of 38°C and 60% relative humidity with Tre reaching 39.8°C during exercise. Before (control) and after each intervention, voluntary activation and force production capacity were evaluated by superimposing an electrically stimulated tetanus during a 45-s MVC. Force production decreased immediately after PaH and ExH compared with control, with the magnitude of decline being more pronounced after ExH (P < 0.01). Mean voluntary activation was also significantly depressed after both interventions (P < 0.01 vs control). However, the extent of decline in voluntary activation was maintained at ∼90% during both PaH and ExH MVC. This decline accounted for 41.5% (PaH) and 33.1% (ExH) of the decrease in force production. In addition, exhaustion coincided with a marked increase in HR (∼96% of maximum) and a decline in stroke volume (25%) and mean arterial pressure (10%) (P < 0.05). The loss of force production capacity during hyperthermia originated from central and peripheral fatigue factors, with the combination of heat stress and previous contractile activity exacerbating the rate of decline. Thus, the observed significant rise in thermal strain in ExH and PaH impaired neuromuscular function and was associated with an exercise performance limiting increase in cardiovascular strain.

Traumatic Brain Injury in Mice Lacking the K Channel, TREK-1

The purpose of this study was to determine whether the potassium channel, TREK-1, was neuroprotective after traumatic brain injury (TBI). Since there are no selective blockers, we used TREK-1 knockout (KO) mice for our study. Wild-type (WT) and TREK-1 KO mice were anesthetized and subjected to controlled-cortical impact injury (deformation of the brain by 1.5 mm by a 3-mm diameter rod traveling at a 3 m/s). Laser Doppler perfusion (LDP) decreased by ∼80% in the injured cortex and remained at that level in both WT and TREK-1 KO mice (n=10 and 11, respectively). Laser Doppler perfusion decreased by 50% to 60% in cortical areas directly adjacent to the site of injury. There were no statistical differences in LDP between genotype. The contusion volume, determined 15 days after the TBI using hematoxylin and eosin-stained coronal brain sections, was 4.1±0.8 (n=10) and 5.1±0.5 (n=11) mm(3) for WT and TREK-1 KO, respectively (not significant, P=0.34). Cell counts of viable neurons in the CA1 and CA3 regions of the hippocampus were similar between WT and TREK-1 KO mice (P=0.51 and 0.84 for CA1 and CA3, respectively). We conclude that TREK-1 expression does not provide brain protection after TBI.

Assessments of skin and tongue microcirculation reveals major changes in porcine sepsis

To examine the relation between central hemodynamics, clinical severity and microvascular findings in tongue and skin during sepsis. Skin and tongue microcirculation was examined using laser Doppler and video microscopy techniques before and 200 min after inducing sepsis in pigs (n=6) by inactivated Neisseria meningitides and in two control animals. All infected pigs developed clinical signs of sepsis. Pericapillary bleedings developed in the tongue in the two pigs with the most severe disease. Capillary density increased in the groin skin in infected pigs after 200 min as compared to baseline (P<0·02). In the same period, mean capillary flow velocity was reduced in groin skin and tongue in septic pigs (P<0·02). At 200 min a fraction of capillaries had developed 'no flow' or 'brisk flow', patterns hardly seen at baseline. Laser Doppler perfusion was reduced in ear and tongue after 200 min (P<0·02 for both). The described pathology was more pronounced in the pigs with the most severe sepsis. Capillary bleedings may be used as an early indication of severe sepsis. Examination of skin and tongue microcirculations may be used to characterize severity of sepsis and possibly to assess effect of treatment.

The effects of low-frequency pulsed electromagnetic fields on microcirculation angiogenesis in acute hindlimb ischemia among diabetic rats

Objective To observe the effects of low-frequency pulsed electromagnetic fields (LFPEMFs) on microcirculation angiogenesis in the hindlimbs of diabetic rats with acute ischemia. Methods Models of acute hindlimb ischemia were established in 60 male Sprague-Dawley diabetic rats. The diabetes model was established using 60 mg/kg intraperitoneal injections of streptozotocin (STZ). Fasting blood glucose levels were greater than 300 mg/dL. The rats were randomly divided into experimental and control groups. The rats in the experimental group were exposed to low-frequency pulsed electromagnetic fields for 2 hours each day, while the control group was not given any treatment. Laser-Doppler perfusion was used to measure blood flow in the ischemic hindlimb on days 0,7, 14 and 28 after the operation. The immunofluorescence of rat endothelial cell antigen-1 ( RECA-1) was used to evaluate the changes in angiogenesis. The levels of vascular endothelial growth factor (VEGF) and fibroblast growth factor-2 (FGF-2) were determined by both Western blotting and ELISA, and VEGFR2 and FGFR1 levels in the ischemic skeletal muscle were determined by Western blotting on days 7, 14 and 28 after the operation. Results The average perfusion ratio was significantly greater in the experimental group at days 14 and 28 compared with the control group. RECA-1 density in the tissues had increased significantly in the experimental group at the 14th and 28th day. The same was observed for FGF-2 and its receptor, but there was no significant difference for VEGF or its receptor in either group. Conclusions LFPMEFs can promote angiogenesis in acute hindlimb ischemia of diabetic rats by up-regulating FGF-2. This suggests that LFPMEFs may be useful for preventing and treating lower limb ischemia in diabetic humans. Key words: Low-frequency pulsed electromagnetic fields; Ischemia; Angiogenesis; Endothelial cell antigen-1 ; Fibroblast growth factor-2

Embryonic Stem Cell–Derived Endothelial Cells Engraft Into the Ischemic Hindlimb and Restore Perfusion

We examined the effect of delivery modality on the survival, localization, and functional effects of exogenously administered embryonic stem cells (ESCs) or endothelial cells derived from them (ESC-ECs) in the ischemic hindlimb. Murine ESCs or ESC-ECs were stably transduced with a construct for bioluminescence imaging (BLI) and fluorescent detection. In a syngeneic murine model of limb ischemia, ESCs or ESC-ECs were delivered by intramuscular (IM), intrafemoral artery (IA), or intrafemoral vein injections (n=5 in each group). For 2 weeks, cell survival and localization were tracked by BLI and confirmed by immunohistochemistry, and functional improvement was assessed by laser Doppler perfusion. BLI showed that ESCs localized to the ischemic limb after IM or IA, but not after intrafemoral vein administration. Regardless of the route of administration, ESCs were detected outside the hindlimb circulation in the spleen or lungs. ESCs did not improve limb perfusion and generated teratomas. In contrast, ESC-ECs delivered by all 3 modalities localized to the ischemic limb, as assessed by BLI. Most surprisingly, ESC-EC injected intrafemoral vein eventually localized to the ischemic limb after initially lodging in the pulmonary circulation. Immunohistochemical studies confirmed the engraftment of ESC-ECs into the limb vasculature after 2 weeks. Notably, ESC-ECs were not detected in the spleen or lungs after 2 weeks, regardless of route of administration. Furthermore, ESC-ECs significantly improved limb perfusion and neovascularization compared with the parental ESCs or the vehicle control group. In contrast to parental ESCs, ESC-ECs preferentially localized in the ischemic hindlimb by IA, IM, and intrafemoral vein delivery. ESC-ECs engrafted into the ischemic microvasculature, enhanced neovascularization, and improved limb perfusion.

The Intrinsic Renal Compartment Syndrome: New Perspectives in Kidney Transplantation

Inflammatory edema after ischemia-reperfusion may impair renal allograft function after kidney transplantation. This study examines the effect of edema-related pressure elevation on renal function and describes a simple method to relieve pressure within the renal compartment. Subcapsular pressure at 6, 12, 24, 48 hr, and 18 days after a 45 min warm ischemia was determined in a murine model of renal ischemia-reperfusion injury. Renal function was measured by Tc-MAG3 scintigraphy and laser Doppler perfusion. Structural damage was assessed by histologic analysis. As a therapeutic approach, parenchymal pressure was relieved by a standardized circular 0.3 mm incision at the lower pole of the kidney capsule. Compared with baseline (0.9+/-0.3 mm Hg), prolonged ischemia was associated with a sevenfold increase in subcapsular pressure 6 hr after ischemia (7.0+/-1.0 mm Hg; P<0.001). Pressure levels remained significantly elevated for 24 hr. Without therapy, a significant decrease in functional parameters was found with considerably reduced tubular excretion rate (33+/-3.5%, P<0.001) and renal perfusion (64.5+/-6.8%, P<0.005). Histologically, severe tissue damage was found. Surgical pressure relief was able to significantly prevent loss of tubular excretion rate (62.5+/-6.8%, P<0.05) and renal blood flow (96.2+/-4.8%; P<0.05) and preserved the integrity of renal structures. Our data support the hypothesis of the existence of a renal compartment syndrome as a consequence of ischemia-reperfusion injury. Surgical pressure relief effectively prevented functional and structural renal impairment, and we speculate that this approach might be of value for improving graft function after renal transplantation.

Laser-Doppler spectrum decomposition applied for the estimation of speed distribution of particles moving in a multiple scattering medium

Recently, a method for the estimation of speed distribution of particles moving in an optically turbid medium has been proposed. The method allows potentially absolute measurement of speed of the particles and can be applied in laser-Doppler perfusion measurements. However, the decomposition technique was limited to short source–detector separations for which the assumption that one photon is Doppler scattered not more than once is fulfilled. In the present paper we show a generalized decomposition technique in which photons can be scattered more than once. We show the theoretical background for decomposition in such a case. We apply a decomposition method for the analysis of laser-Doppler spectra obtained by Monte Carlo simulations. This analysis allows showing noise limits in which the technique can be effectively applied in analysis of measured spectra. We propose an approximated scattering model based on the assumption that for one photon consecutive Doppler scattering events occur on particles moving with the same speed, and we show that this approximation does not influence significantly the uncertainty of the resulting speed distribution. The proposed decomposition procedure is validated in measurements on a physical flow model. The decomposition procedure is also validated by analysis of spectra measured on a physical phantom using laser-Doppler flow meter (Oxford Optronix, UK). A diluted solution of milk was pumped through a tube fixed in an optically turbid material with speed varying from 0 mm s−1 to 4 mm s−1. We observed a linear relation between actual speed of milk solution and speed estimated from results of spectra decomposition.

Electroacupuncture Induces Differential Effects between Yin and Yang: A Study using Cutaneous Blood Flow and Temperature Recordings of the Hand's Dorsum and Palm

The underlying theory of traditional Chinese Medicine (TCM) considers that Yin and Yang are in the opposition with each other and play different roles in physiological responses. Several studies have reported that electroacupuncture (EA) produces a greater effect than manual acupuncture (MA), and that the effect of EA is similar to transcutaneous electric nerve stimulation (TENS). Therefore, the purpose of the present study was to investigate the differences between Yin and Yang induced by acupuncture. A total of 20 healthy volunteers were studied. The cutaneous blood flow and temperature were recorded by a laser doppler perfusion and temperature monitoring system on the dorsum and palm of the right hand. Four sessions of sham acupuncture (SA), MA, 2 Hz EA, and 2 Hz TENS were bilaterally applied to Zusanli (ST36) and Shangjuxu (ST37) acupoints. Each of the subjects received four sessions in a random manner. The treatment interval was at least three days between sessions in order to prevent overlapping residual effects. Each of the four sessions was divided into pre-acupuncture period (BP), acupuncture period (AP), and post-acupuncture (PP) periods. Each treatment period was 15 min. Results indicated that the cutaneous blood flow recorded from the palm of the hand were greater than that recorded from the dorsum at the pre-acupuncture period; while the difference in the cutaneous temperature from the dorsum of the hand between AP and BP was greater in the 2 Hz EA session than in the SA and MA sessions. In conclusion, the results of the present study were consistent with the underlying theory of TCM that considers the fundamental differences between Yin and Yang.

Time Development Models for Perfusion Provocations Studied with Laser-Doppler Flowmetry, Applied to Iontophoresis and PORH

Clinical acceptance of laser-Doppler perfusion monitoring (LDPM) of microcirculation suffers from lack of quantitatively reliable signal data, due to varying tissue constitution, temperature, hydration, etc. In this article, we show that a novel approach using physiological models for response upon provocations provides quantitatively and clinically relevant time constants. We investigated this for two provocation protocols: postocclusive reactive hyperemia (PORH) and iontophoresis shots, measured with LDPM on extremities. PORH experiments were performed on patients with peripheral arterial occlusive disease (PAOD) or diabetes mellitus (DM), and on healthy controls. Iontophoresis experiments were performed on pre-eclamptic patients and healthy controls. We developed two dynamical physical models, both based on two characteristic time constants: for PORH, an "arterial" and a "capillary" time constant and, for iontophoresis, a "diffusion" and a "decay" time constant. For the different subject groups, we could extract time constants that could probably be related to physiological differences. For iontophoresis, a shot saturation constant was determined, with very different values for different groups and administered drugs. With these models, the dynamics of the provocations can be investigated and quantitative comparisons between experiments and subject groups become available. The models offer a quantifiable standard that is independent of the type of LDPM instrumentation.

Evaluation of microvascular endothelial function in patients with type 1 diabetes using laser-Doppler perfusion monitoring: Which method to choose?

The evaluation of microvascular function is essential in the investigation of the pathophysiology of cardiometabolic diseases [ Struijker-Boudier, H.A. et al., 2007. Evaluation of the microcirculation in hypertension and cardiovascular disease. Eur. Heart J. 28, 2834–2840]. In clinical research and practice, the study of microcirculation is of great value in the assessment of the effects of medical interventions and monitoring disease progression. It is well-known that patients with type 1 and 2 diabetes have microvascular dysfunction that results from numerous factors including hyperglycemia, oxidative stress and insulin resistance [ Schalkwijk, C.G., Stehouwer, C.D., 2005. Vascular complications in diabetes mellitus: the role of endothelial dysfunction. Clin. Sci. (Lond). 109, 143–159]. Moreover, skin microvascular dysfunction in type 1 diabetes precedes symptoms of end-organ microvascular disease [Khan, F. et al., 2000. Impaired skin microvascular function in children, adolescents, and young adults with type 1 diabetes. Diabetes Care 23, 215–220]. In this study, we assessed skin microvascular function of patients with type 1 diabetes using laser-Doppler perfusion monitoring (LDPM) coupled with physiological and pharmacological local vasodilator stimuli.

Diffusion model for iontophoresis measured by laser-Doppler perfusion flowmetry, applied to normal and preeclamptic pregnancies

We present a physical model to describe iontophoresis time recordings. The model is a combination of monodimensional material diffusion and decay, probably due to transport by blood flow. It has four adjustable parameters, the diffusion coefficient, the decay constant, the height of the response, and the shot saturation constant, a parameter representing the relative importance of subsequent shots (in case of saturation). We test the model with measurements of blood perfusion in the capillary bed of the fingers of women who recently had preeclampsia and in women with a history of normal pregnancy. From the fits to the measurements, we conclude that the model provides a useful physical description of the iontophoresis process.

Interanimal variability in preexisting collaterals is a major factor determining outcome in experimental angiogenesis trials

Despite numerous animal trials reporting that cell therapy promotes collateral flow, clinical trials have not convincingly shown benefit. Patient-related risk factors are often used to explain these discrepancies. However, during the course of our own angiogenesis studies using mice, we noted large anatomical variability in collateral vessels. The purpose of the present investigation was to define how important this factor might be in determining intervention outcomes. Hindlimb ischemia was induced in BALB/c mice by ligating the superficial femoral artery. After 24 h, animals were treated by injecting the adductor muscle with either control media or cultured mesenchymal stem cells (MSCs). Blood flow recovery was measured using laser-Doppler [laser-Doppler perfusion imaging (LDPI) ratio]. In a second experiment, mice were stratified 24 h after arterial ligation before treatment by using a simple clinical score of the ligated leg: 1, able to flex, mild discoloration; 2, no flexion, mild discoloration; 3, severe discoloration; and 4, any necrosis. Without stratification, blood flow recovery significantly increased in the MSC-treated group (P < 0.05, n = 6 MSC group, n = 7 media group). In the experiment employing stratification, all differences between the groups disappeared (n = 11 MSC group, n = 10 media group; P = 0.3). Furthermore, we found a striking inverse correlation between clinical score on day 1 and the LDPI ratio on day 28 (P < 0.0001; n = 79). Anatomical confirmation of the disparity in preexisting collaterals was found in two different mouse strains using microscopic computed tomography. In conclusion, there is substantial interanimal variability in preexisting collateral flow, and this variability can importantly influence outcome. To overcome this, either animals must be stratified before treatment, the number of animals must be increased substantially, or, preferably, both.

Relationships between Physical Fitness and Endothelial Vascular Control in Elderly Men and Women

This study investigates correlations between physical fitness and endothelial vascular control and its underlying mechanisms in older men and women. A total of 38 healthy older adults (18 men, age 72.2±3.2 yr; 18 women, age 73.5±2.8 yr) were studied. All subjects received a three-minute step test to determine their cardiopulmonary index (CPI). Both percentage of body fat and distribution of body water, including total body water, intracellular water (ICW), and intracellular water (ECW), were measured by bioelectrical impedance analysis. Hemodynamic characteristics in the arterial and venous vessel were analyzed by impedance plethysmography, whereas skin vascular endothelial function was measured using a laser Doppler perfusion with iontophoresis. Our results showed that 1) hyperemic arterial flow, acetylcholine (ACh)-induced cutaneous perfusion, and the ratio of ACh to sodium nitroprusside (SNP)-induced cutaneous perfusion was positively correlated with CPI in both older men and women; 2) a lower CPI was accompanied by a higher ECW/ICW ratio in older women (r= −0.580), while a higher CPI was associated with a lower body fat in older men (r= −0.496); and 3) the ratio of ACh to SNP-induced cutaneous perfusion was negatively correlated with the ECW/ICW ratio in the female subjects(r= −0.538) and the body fat in the male subjects (r= −0.445). We conclude that endothelial vascular function can influence cardiopulmonary fitness in the elderly. Moreover, the age-related declines of physical fitness and endothelium-dependent vasodilation may be associated with the sex-related changes in body water distribution and fat percentage.