Evaluation of sympathetic adrenergic branch of cutaneous neural control throughout thermography and its relationship to nitric oxide levels in patients with fibromyalgia.

BACKGROUND: Fibromyalgia syndrome is defined as a complex disease, characterized by chronic widespread musculoskeletal pain and other symptoms. The factors underlying physiopathology of fibromyalgia are not well understood, complicating its diagnosis and management. OBJECTIVES: To evaluate the peripheral vascular blood flow of the skin of the hands and the core body temperature as indirect measures of sympathetic adrenergic activity of the nervous system and its relationship to nitric oxide levels (NO) in women with fibromyalgia compared with healthy controls. METHODS: Forty-two women with fibromyalgia and 52 healthy women were enrolled in this observational pilot study. We used infrared thermography of the hands and an infrared dermal thermometer to evaluate the peripheral vascular blood flow and tympanic and axillary core body temperature, respectively. We measured NO levels using the ozone chemiluminescence-based method. RESULTS: Two-way analysis of covariance (ANCOVA) showed that the tympanic (P=0.002) and hand temperatures were significantly higher in the patients with fibromyalgia than in the controls (P≤0.001). Significant associations were also found between serum NO levels and minimum temperatures at the dorsal center of the dominant hand (ß=-3.501; 95% confidence interval [CI] -6.805, ­0.198; P= 0.038), maximum temperature (ß=-5.594; 95% CI ­10.106, ­1.081; P=0.016), minimum temperature (ß=-4.090; 95% CI ­7.905, ­0.275; P=0.036), and mean temperature (ß=-5.519; 95% CI ­9.933, ­1.106; P=0.015) of the center of the palm of the non-dominant hand, maximum temperature at the thenar eminence of the dominant hand (ß=-5.800; 95% CI ­10.508, ­1.092; P=0.017), and tympanic temperature (ß=-9.321; 95% CI ­17.974, ­0.669; P=0.035) in the controls. CONCLUSIONS: Our findings indicate that the women with fibromyalgia showed higher tympanic core body and hand temperature than the healthy controls. Moreover, there were negative associations between hand peripheral vasodilation and NO in the healthy women but not in those with fibromyalgia, suggesting a dysfunction of sympathetic cutaneous neural control.

A novel method to quantify cutaneous vascular innervation.

INTRODUCTION: To develop a new method to quantify the density of nerves, vessels, and the neurovascular contacts, we studied skin biopsies in diabetes and control subjects. METHODS: Skin biopsies with dual immunofluorescent staining were used to visualize nerves and blood vessels. The density of nerves, vessels, and their neurovascular contacts were quantified with unbiased stereology. Results were compared with examination findings, validated questionnaires, and autonomic function. RESULTS: In tissue from 19 controls and 20 patients with diabetes, inter-rater and intra-rater intraclass correlation coefficients were high (>0.85; P < .001) for all quantitative methods. In diabetes, the nerve densities (P < .05), vessel densities (P < .01), and the neurovascular densities (P < .01) were lower compared with 20 controls. Results correlated with autonomic function, examination and symptom scores. DISCUSSION: We report an unbiased, stereological method to quantify the cutaneous nerve, vessel and neurovascular density and offer new avenues of investigation into cutaneous neurovascular innervation in health and disease.

Glabrous and non-glabrous vascular responses to mild hypothermia.

This study examined cutaneous vasoconstriction to whole-body hypothermia, specifically contributions of neural and endothelial vasomotor responses in glabrous and non-glabrous skin. Eleven participants were semi-recumbent at an ambient temperature of 22 °C for 30 min, after which ambient temperature was decreased to 0 °C until rectal temperature (Tre) had decreased by 0.5 °C. Laser-Doppler fluxmetry was measured at the forehead and thigh for measures of glabrous and non-glabrous skin, respectively; wavelet analysis was performed on the laser-Doppler signal to determine endothelial and neural activities. Hypothermia took on average 97 ±â€¯7 min and caused marked decreases at glabrous (42 ±â€¯5%baseline, p < 0.001) and non-glabrous (69 ±â€¯4%baseline, p < 0.001) skin. In glabrous skin, neural activity increased from 11 ±â€¯1% at thermoneutral to 18 ±â€¯1% (p < 0.001). In non-glabrous skin there was an initial decrease (p = 0.001) in neural activity from 13 ±â€¯2% to 9 ±â€¯1% (-0.2 °C decrease in Tre) and then increased (p = 0.002) to 21 ±â€¯2% baseline at -0.5 °C Tre. Endothelial activity decreased in both glabrous (16 ±â€¯3% to 6 ±â€¯1%, p < 0.001) and non-glabrous (15 ±â€¯1% to 7 ±â€¯1%, p = 0.003) skin. Hypothermia elicits large decreases in skin blood flow in both glabrous and non-glabrous skin that are related to increases in neural activity and a reduction of endothelial activity.

Robust Increase in Supply by Vessel Dilation in Globally Coupled Microvasculature.

Neuronal activity induces changes in blood flow by locally dilating vessels in the brain microvasculature. How can the local dilation of a single vessel increase flow-based metabolite supply, given that flows are globally coupled within microvasculature? Solving the supply dynamics for rat brain microvasculature, we find one parameter regime to dominate physiologically. This regime allows for robust increase in supply independent of the position in the network, which we explain analytically. We show that local coupling of vessels promotes spatially correlated increased supply by dilation.

Postsynaptic cutaneous vasodilation and sweating: influence of adiposity and hydration status.

INTRODUCTION: Obesity and hypohydration independently affect postsynaptic endothelial function, but it is unknown if hypohydration affects lean and obese individuals differently. PURPOSE: To examine the effect of hypohydration on postsynaptic cutaneous vasodilation and sweating in men with high and low adiposity (HI- and LO-BF, respectively). METHODS: Ten males with LO-BF and ten with HI-BF were instrumented for forearm microdialysis when euhydrated and hypohydrated. Changes in cutaneous vascular conductance (CVC) with intradermal infusion of sodium nitroprusside (SNP) and methacholine chloride (MCh) were assessed. Local sweat rate (LSR) was simultaneously assessed at the MCh site. At the end of the last dose, maximal CVC was elicited by delivering a maximal dose of SNP for 30 min to both sites with simultaneous local heating at the SNP site. The concentration of drug needed to elicit 50% of the maximal response (EC50) was compared between groups and hydration conditions. RESULTS: When euhydrated, EC50 of MCh-induced CVC was not different between LO- vs. HI-BF [- 3.04 ± 0.12 vs. - 2.98 ± 0.19 log (MCh) M, P = 0.841]. EC50 of SNP-induced CVC was higher in euhydrated HI- vs. LO-BF (- 1.74 ± 0.17 vs. - 2.13 ± 0.06 log (SNP) M, P = 0.034). Within each group, hydration status did not change MCh- or SNP-induced CVC (P > 0.05). LSR was not different between groups or hydration condition (P > 0.05). CONCLUSIONS: These data suggest reduced sensitivity of endothelium-independent vasodilation in individuals with high adiposity when euhydrated. However, hypohydration does not affect cutaneous vasodilation or local sweat rate differently between individuals with low or high adiposity.

Impaired neurovascular reactivity in the microvasculature of pregnant women with preeclampsia.

INTRODUCTION: PE is associated with maternal vascular dysfunction, leading to serious cardiovascular risk both during and following pregnancy. OBJECTIVE: To assess microvascular reactivity in pregnant women with PE. METHODS: A cross-sectional study was performed in 36 pregnant women with PE and 36 normotensive pregnant women (C) in the third trimester. Skin microvascular blood flow was measured using LDF at rest (RF), during the maximum hyperemic response to brief arterial occlusion (MF) and during the sympathetically mediated constrictor response to deep IBH. RESULTS: In pregnant women with PE, RF was higher [C, 8.1 (4.6); PE, 12.0 (7.6), P<.001; PU perfusion units; median (IQR)] and MF/RF [C, 6.1 (3.7); PE, 3. 9 (4.9) P<.001] and peak CVC lower (P=.009) compared to normotensive controls. The constrictor response to IBH [C, 62.4% (27.9); PE, 33.0% (50.6), P=.008] was reduced in women with PE. In univariate analysis, MF/RF was associated with PE status (r=-.417, P=.0001), systolic (r=-.385, P=.001), and diastolic (r=-.388, P=.001) blood pressure, but not BMI (r=.077, P=.536). CONCLUSIONS: Women with PE are more than three times more likely to exhibit a reduced microvascular reactivity in the third trimester of pregnancy than normotensive pregnant controls. These differences may be attributable in part to an altered sympathetic neural microvascular tone in PE.

Mechanisms and time course of menthol-induced cutaneous vasodilation.

Menthol is a vasoactive compound that is widely used in topical analgesic agents. Menthol induces cutaneous vasodilation, however the underlying mechanisms are unknown. Determining the rates of appearance and clearance of menthol in the skin is important for optimizing topical treatment formulation and dosing. The purpose of this study was to determine the mechanisms contributing to menthol-mediated cutaneous vasodilation and to establish a time course for menthol appearance/clearance in the skin. Ten young (23±1years, 5 males 5 females) subjects participated in two protocols. In study 1, four intradermal microdialysis fibers were perfused with increasing doses of menthol (0.1-500mM) and inhibitors for nitric oxide (NO), endothelium derived hyperpolarizing factors (EDHFs), and sensory nerves. Skin blood flow was measured with laser Doppler flowmetry and normalized to %CVCmax. In study 2, two intradermal microdialysis fibers were perfused with lactated Ringer's solution. 0.017mL·cm-2 of a 4% menthol gel was placed over each fiber. 5µL samples of dialysate from the microdialysis fibers were collected every 30min and analyzed for the presence of menthol with high performance gas chromatography/mass spectrometry. Skin blood flow (laser speckle contrast imaging) and subjective ratings of menthol sensation were simultaneously obtained with dialysate samples. In study 1, menthol induced cutaneous vasodilation at all doses ≥100mM (all p<0.05). However, inhibition of either NO, EDHFs, or sensory nerves fully inhibited menthol-mediated vasodilation (all p>0.05). In study 2, significant menthol was detected in dialysate 30min post menthol application (0.89ng, p=0.0002). Relative to baseline, cutaneous vasodilation was elevated from minutes 15-45 and ratings of menthol sensation were elevated from minute 5-60 post menthol application (all p<0.05). Menthol induces cutaneous vasodilation in the skin through multiple vasodilator pathways, including NO, EDHF, and sensory nerves. Topical menthol is detectable in the skin within 30min and is cleared by 60min. Skin blood flow and perceptual measures follow a similar time course as menthol appearance/clearance.

Nerve growth factor facilitates perivascular innervation in neovasculatures of mice.

It is well known that blood vessels including arterioles have a perivascular innervation. It is also widely accepted that perivascular nerves maintain vascular tone and regulate blood flow. Although there are currently prevailing opinions, unified views on the innervation of microcirculation in any organs have not been established. The present study was designed to investigate whether there are perivascular nerves innervated in microvessels and neovessels. Furthermore, we examined whether nerve growth factor (NGF) can exert a promotional effect on perivascular nerve innervation in neovessels of Matrigel plugs. A Matrigel was subcutaneously implanted in mouse. The presence of perivascular nerves in Matrigel on Day 7-21 after the implantation was immunohistochemically studied. NGF or saline was subcutaneously administered by an osmotic mini-pump for a period of 3-14 days. The immunostaining of neovasculatures in Matrigel showed the presence of perivascular nerves on Day 21 after Matrigel injection. Perivascular nerve innervation of neovessels within Matrigel implanted in NGF-treated mice was observed in Day 17 after Matrigel implantation. However, NGF treatment did not increase numbers of neovessels in Matrigel. These results suggest that perivascular nerves innervate neovessels as neovasculatures mature and that NGF accelerates the innervation of perivascular nerves in neovessels.

[MODULATION OF LACTATE PRODUCTION, TRANSPORT AND RECEPTION BY CELLS IN THE MODEL OF BRAIN NEUROVASCUL. UNIT I.]

Metabolic activity of cells within a neurovascular unit is among the factors determining structural and functional integritY of the blood-brain barrier and the an- giogenesis process. in order to verify the hypothesis about the role Of g1YcolYtic activity in the perivascula astroglialcells associated with lactate release in the development of functioning of cerebral microvessel endothelial cells, we have used a three-component model of the brain neurovascular unit in vitro. The cells o f n o n -en d o th elia l o rig in w ere in c u b a te d in th e p rese n ce o f m o d u la to rs o f la c ta te pro d u c n ago ni glu c ose ta a G ly c o s o) , bas t h e oe t a n t a at- blocker of monocarboxylate transporters MCTlprCT and recepltiors of3Ctate0produasan (2-donisyoflactate G e8 breceptor) Iasa estbishe vthat that te suppression of lactate production and transport, prdc o1,adrcpin(C-O-Aa n (2gdoxysgflucoase as a glycolysis inhibitor), transport (phloretin as a sukr of lacaroduto transport , aswellasastimultionof3lactate receptors in astroglial cells, lead to aberrant development of endothelial layer, ther by u g g e tin t h efor atio o f anti ngi gencmi roen ircm ent for cerebral endothelium due to inappropriate lactate-m ediated effects. KeYw.ords:-n-eur-ovascular unit; metabolism; glYcolysis; lactate.

Characterization of Perivascular Nerve Distribution in Rat Mesenteric Small Arteries.

The distribution pattern of perivascular nerves in some branches of rat mesenteric arteries was studied. Mesenteric arteries isolated from 8-week-old Wistar rats were divided into the 1st-, 2nd-, and 3rd-order branches. The distribution of perivascular nerves in each branch was immunohistochemically evaluated using antibodies against neuropeptide Y (NPY), tyrosine hydroxylase (TH), calcitonin gene-related peptide (CGRP), substance P (SP), and neuronal nitric oxide synthase (nNOS). The density of NPY-, TH-, CGRP-, and SP-like immunoreactive (LI) nerves in the 2nd and 3rd branches was significantly greater than that in the 1st branch, and a negative relationship was found between nerve density and arterial diameter, except for TH-LI nerves. The density of NPY- and TH-LI nerves in all branches, which was similar, was greater than that of CGRP- (except for NPY-LI nerves in the 1st branch), SP-, or nNOS-LI nerves. Double immunostaining revealed that TH-LI nerves made contact with nNOS-LI, CGRP-LI, and SP-LI nerves and that CGRP-LI nerves made contact with TH-, NPY-, or nNOS-LI nerves, while TH-LI and CGRP-LI nerves nearly merged with NPY-LI and SP-LI nerves, respectively. These results suggest that the each branch of mesenteric arteries is densely innervated by vasoconstrictor nerves containing NPY, TH, and vasodilator CGRP nerves. They also suggest that the intense density of perivascular nerves in the 2nd and 3rd branches may contribute to maintaining vascular tone.

Nerve growth factor stimulates regeneration of perivascular nerve, and induces the maturation of microvessels around the injured artery.

An immature vasa vasorum in the adventitia of arteries has been implicated in induction of the formation of unstable atherosclerotic plaques. Normalization/maturation of the vasa vasorum may be an attractive therapeutic approach for arteriosclerotic diseases. Nerve growth factor (NGF) is a pleotropic molecule with angiogenic activity in addition to neural growth effects. However, whether NGF affects the formation of microvessels in addition to innervation during pathological angiogenesis is unclear. In the present study, we show a new role for NGF in neovessels around injured arterial walls using a novel in vivo angiogenesis assay. The vasa vasorum around arterial walls was induced to grow using wire-mediated mouse femoral arterial injury. When collagen-coated tube (CCT) was placed beside the injured artery for 7-14 days, microvessels grew two-dimensionally in a thin layer on the CCT (CCT-membrane) in accordance with the development of the vasa vasorum. The perivascular nerve was found at not only arterioles but also capillaries in the CCT-membrane. Biodegradable hydrogels containing VEGF and NGF were applied around the injured artery/CCT. VEGF significantly increased the total length and instability of microvessels within the CCT-membrane. In contrast, NGF induced regeneration of the peripheral nerve around the microvessels and induced the maturation and stabilization of microvessels. In an ex vivo nerve-free angiogenesis assay, although NGF potentially stimulated vascular sprouting from aorta tissues, no effects of NGF on vascular maturation were observed. These data demonstrated that NGF had potent angiogenic effects on the microvessels around the injured artery, and especially induced the maturation/stabilization of microvessels in accordance with the regeneration of perivascular nerves.

Eyeing central neurons in vascular growth and reparative angiogenesis.

The generation of blood vessels is a highly synchronized process requiring the coordinated efforts of several vascular and nonvascular cell populations as well as a stringent orchestration by the tissue being vascularized. Stereotyped angiogenesis is vital for both developmental growth and to restore tissue metabolic supply after ischemic events. Central neurons such as those found in the brain, spinal cord, and retina are vast consumers of oxygen and nutrients and therefore require high rates of perfusion by functional vascular networks to ensure proper sensory transmission. During a metabolic mismatch, such as that occurring during a cerebrovascular infarct or in ischemic retinopathies, there is increasing evidence that central neurons have an inherent ability to influence the vascular response to injury. With a focus on the retina and retinal ischemic disorders, this review explores the ever-growing evidence suggesting that central neurons have the propensity to impact tissue vascularization and reparative angiogenesis. Moreover, it addresses the paradoxical ability of severely ischemic neurons to hinder vascular regrowth and thus segregate the most severely injured zones of nervous tissue. The topics covered here are pertinent for future therapeutic strategies because promoting and steering vascular growth may be beneficial for ischemic disorders.

Noninvasive examination of endothelial, sympathetic, and myogenic contributions to regional differences in the human cutaneous microcirculation.

The aim of this study was to examine whether there are regional differences in the cutaneous microvascular responses of the forearm and the leg. Utilizing a non-invasive measure (spectral analysis),we looked at the influence of the endothelial, sympathetic, and myogenic function between regions at thermoneutral conditions (33 °C) and in response to local skin warming (42 °C) using laser-Doppler flowmetry (LDF). We recruited 18 young, healthy participants, who visited the lab on 2 separate occasions. Participants were instrumented with LDF probes and local skin heater probe-holders, placed on the forearm or the leg. Blood pressure was recorded by oscillometry. At both 33 °C and during local skin warming to 42 °C, skin vasomotion for the forearm and leg were evaluated using spectral analysis of the LDF recordings. There were significant differences among all frequencies of interest between the forearm and the leg. At 33 °C the leg presented with higher (P=0.003) activity for endothelial (0.009-0.021 Hz), sympathetic (P=0.002) (0.021-0.052 Hz), and myogenic (P=0.004) (0.052-0.145 Hz) activity when compared to the forearm. In contrast, following 35 min of local skin warming, the forearm had greater endothelial (P=0.019), sympathetic (P=0.006), and myogenic (P=0.005) vasomotion than the leg. These outcomes indicate regional differences in the cutaneous microcirculation. The current results are similar to our previous work using invasive methods and pharmacological agents, indicating that non-invasive analyses may be useful in the diagnoses and understanding of the mechanisms that control the microvascular function of pathological conditions.

Imaging of the islet neural network.

The islets of Langerhans receive signals from the circulation and nerves to modulate hormone secretion in response to physiological cues. Although the rich islet innervation has been documented in the literature dating as far back as Paul Langerhans' discovery of islets in the pancreas, it remains a challenging task for researchers to acquire detailed islet innervation patterns in health and disease due to the dispersed nature of the islet neurovascular network. In this article, we discuss the recent development of 3-dimensional (3D) islet neurohistology, in which transparent pancreatic specimens were prepared by optical clearing to visualize the islet microstructure, vasculature and innervation with deep-tissue microscopy. Mouse islets were used as an example to illustrate how to apply this 3D imaging approach to characterize (i) the islet parasympathetic innervation, (ii) the islet sympathetic innervation and its reinnervation after transplantation under the kidney capsule and (iii) the reactive cellular response of the Schwann cell network in islet injury. While presenting and characterizing the innervation patterns, we also discuss how to apply the signals derived from transmitted light microscopy, vessel painting and immunostaining of neural markers to verify the location and source of tissue information. In summary, the systematic development of tissue labelling, clearing and imaging methods to reveal the islet neuroanatomy offers insights to help study the neural-islet regulatory mechanisms and the role of neural tissue remodelling in the development of diabetes.

Distribution of substance P and the calcitonin gene-related peptide in the human tensor tympani muscle.

Substance P-immunoreactive nerve fiber (SP-IR NF) and calcitonin gene-related peptide-immunoreactive nerve fiber (CGRP-IR NF) are important mediators of neurogenic inflammation and blood supply. SP-IR and CGRP-IR NFs in the tensor tympani muscle (TTM) of the human middle ear have yet to be described. In this study, the TTM, tympanic membrane, malleus in the middle ear and tensor veli palatini muscle (TVPM) were examined by whole-mount immunohistochemistry in tissue from Japanese subjects. Thirteen human cadavers (ranging in age from 46 to 90 years) were used in this study. SP-IR and CGRP-IR NFs were primarily found on vessels at the origin, insertion and belly of the surface of the TTM and on the internal surface of the tympanic membrane. These neural factors were also detected on the surface of the malleus and the insertion of the TVPM. Therefore, our results indicate that existence of the SP-IR and CGRP-IR NFs of the TTM and the TVPM may reflect muscle properties involved in pain or inflammation of the middle ear.

Sympathetic innervation does not contribute to glycerol release in ischemic flaps.

BACKGROUND: Extracellular glycerol as detected by microdialysis has been used as a surrogate marker for (ischemic) tissue damage and cellular membrane breakdown in the monitoring of free microvascular musculocutaneous flaps. One confounding factor for glycerol as a marker of ischemic cell damage is the effect of lipolysis and associated glycerol release as induced by sympathetic signalling alone. We hypothesized that extracellular glycerol concentrations in a microvascular flap with sympathetic innervation would be confounded by intact innervation per se as compared to denervated flap. Clinical relevance is related to the use of both free and pedicled flaps in reconstructive surgery. We tested the hypothesis in an experimental model of microvascular musculocutaneal flaps. METHODS: Twelve pigs were anesthetized and mechanically ventilated. Two identical rectus abdominis musculocutaneal flaps were raised for the investigation. In the A-flaps the adventitia of the artery and accompanying innervation was carefully stripped, while in the B-flaps it was left untouched. Flap ischemia was induced by clamping both vessels for 60 minutes. The ischemia was confirmed by measuring tissue oxygen pressure, while extracellular lactate to pyruvate ratio indicated the accompanying anaerobic metabolism locally. RESULTS: Intramuscular and subcutaneal extracellular glycerol concentrations were measured by microdialysate analyzer. Contrary to our hypothesis, glycerol concentrations were comparable between the two ischemia groups at 60 minutes (p = 0.089, T-test). CONCLUSIONS: In this experimental model of vascular flap ischemia, intact innervation of the flap did not confound ischemia detection by glycerol. Extrapolation of the results to clinical setting warrants further studies.

Impaired transient vasodilation and increased vasoconstriction to digital local cooling in primary Raynaud's phenomenon.

Raynaud's phenomenon (RP) is defined as episodic ischemia of the extremities in response to cold. Although the structure of skin capillaries is normal in primary RP, some data suggest impairment of microvascular function. We aimed at testing whether digital skin blood flow was lower in RP than in controls while cooling locally. We further evaluated the contribution of sensory nerves in the response. We recruited 21 patients with primary RP and 20 healthy volunteers matched on age and gender. After a 10-min baseline at 33°C, skin temperature was cooled at 15 or 24°C during 30 min on the forearm and the finger while monitoring perfusion with a custom-design laser Doppler flowmetry probe. Perfusion was also assessed after topical anesthesia. Blood flow was expressed as cutaneous vascular conductance (CVC). Data were subsequently expressed as area above the curve (AAC(0-30)) of the percentage decrease from baseline CVC (%BL). CVC on the dorsum of the finger was lower in RP patients compared with controls at 15°C (AAC(0-30) were 106,237.2 and 69,544.3%BL·s, respectively; P = 0.02) and at 24°C (AAC(0-30) were 86,915 and 57,598%BL·s, respectively; P = 0.04) whereas we observed no significant difference on the finger pad and the forearm. Topical anesthesia increased CVC in patients with RP (P = 0.05), whereas it did not affect reactivity in controls (P = 0.86). Our study shows exaggerated skin microvascular vasoconstriction to local cooling on the dorsum of the finger in primary RP compared with controls. Part of this abnormal response in primary RP depends on sensitive nerves.

Comparison of laser speckle contrast imaging with laser Doppler for assessing microvascular function.

OBJECTIVE: To compare the inter-day reproducibility of post-occlusive reactive hyperaemia (PORH) and sympathetic vasomotor reflexes assessed by single-point laser Doppler flowmetry (SP-LDF), integrating-probe LDF (IP-LDF) and laser speckle contrast imaging (LSCI), and the spatial variability of PORH assessed by IP-LDF and LSCI. We also evaluated the relationship between IP-LDF and LSCI perfusion values across a broad range of skin blood flows. METHODS: Eighteen healthy adults (50% male, age 27 ± 4 years) participated in this study. Using SP-LDF, IP-LDF and LSCI, indices of skin blood flow were measured on the forearm during PORH (1-, 5- and 10-min occlusions) and on the finger pad during inspiratory gasp and cold pressor tests. These tests were repeated 3-7 days later. Data were converted to cutaneous vascular conductance (CVC; laser Doppler flow/mean arterial pressure) and expressed as absolute and relative changes from pre-stimulus CVC (ΔCVC(ABS) and ΔCVC(REL), respectively), as well as normalised to peak CVC for the PORH tests. Reproducibility was expressed as within-subjects coefficients of variation (CV, in %) and intraclass correlation coefficients. RESULTS: The reproducibility of PORH on the forearm was poorer when assessed with SP-LDF and IP-LDF compared to LSCI (e.g., CV for 5-min PORH ΔCVC(ABS)=35%, 27% and 19%, respectively), with no superior method of data expression. In contrast, the reproducibility of the inspiratory gasp and cold pressor test responses on the finger pad were better with SP-LDF and IP-LDF compared to LSCI (e.g., CV for inspiratory gasp ΔCVC(REL)=13%, 7% and 19%, respectively). The spatial variability of PORH responses was poorer with IP-LDF compared to LSCI (e.g., CV ranging 11-35% versus 3-16%, respectively). The association between simultaneous LSCI and IP-LDF perfusion values was non-linear. CONCLUSION: The reproducibility of cutaneous PORH was better when assessed with LSCI compared to SP-LDF and IP-LDF; probably due to measuring larger skin areas (lower inter-site variability). However, when measuring sympathetic vasomotor reflexes on the finger pad, reproducibility was better with SP-LDF and IP-LDF, perhaps due to the high sensitivity of LSCI to changes in skin blood flow at low levels.

[The level of endothelin-1 and reactivity of skin microvessels in patients with early stages of chronic kidney disease].

AIM: To evaluate endothelin-1 (ET-1) levels and to characterize reflex vasomotor reactions of skin vessels in distant exposure to cold in patients with chronic kidney disease (CKD) of stage I and II. MATERIAL AND METHODS: Glomerular filtration rate (GFR) was calculated by MDRD formula for 40 healthy subjects (mean age 39.2 +/- 2.0 years) and 147 CKD patients (mean age 41.4 +/- 1.8 years). All the patients were also exposed to the cold test (a modified variant). RESULTS: Patients with CKD stage I demonstrated a 35.1% fall in blood flow rate (Qas) in response to cold stimulus, patients of stage II--a 42.2% fall, healthy patients--a 19.3%. CKD patients of stage I and II retained a Qas fall for 3 min after exposure to cold, while healthy subjects resumed skin blood circulation immediately after exposure to cold. Blood plasma ET-1 concentration in healthy subjects was 0.239 +/- 0.055 fmol/ml, in stage I CKD patients--0.334 +/- 0.066 fmol/l, in stage II CKD patients--0.422 +/- 0.041 fmol/l. Relationships were found between ET-1 level and GFR (Rs = 0.242; p < 0.05), 24 h proteinuria (Rs = 0.375; p < 0.003) and Qas% in the cold test (Rs = -0.389; p < 0.003) as well as time of recovery of the background Qas (Rs = -0.311; p < 0.003). CONCLUSION: Dysfunction of autonomic nervous system at early stages of CKD may arise by means of activation of ET-1 synthesis in response to enhancement of sympathetic impacts.

Structural and microvascular changes of the peripapillary retinal nerve fiber layer in Von Hippel-Lindau disease: an OCT and OCT angiography study.

Von Hippel-Lindau (VHL) disease is an autosomal dominant genetic disease caused by VHL gene mutation. Retinal hemangioblastomas (RH) are vascularized tumors and represent the main ocular manifestation of the disease. Histopathologically, RH are composed of capillary vessels and stromal cells, the neoplastic population of the lesion. The origin of these stromal cells remains controversial, even if they are hypothesized to be glial cells. The aim of the present study was to investigate neuronal and microvascular changes of the peripapillary retinal nerve fiber layer, in which glial cells, neurons and capillaries (the radial peripapillary capillary plexus) interact. VHL patients with or without peripheral RH were enrolled and compared to healthy controls. Mean peripapillary retinal nerve fiber layer (pRNFL) thickness was measured by means of optical coherence tomography (OCT). The following vascular parameters of the radial peripapillary capillary plexus were quantified using OCT angiography: Vessel Area Density,Vessel Length Fraction, Vessel Diameter Index and Fractal Dimension. One hundred and nine eyes of 61 patients, and 56 eyes of 28 controls were consecutively studied. Mean pRNFL was significantly thinner in VHL eyes without RH versus eyes with RH and controls. Mean pRNFL thickness did not differ between VHL eyes with RH and controls. All OCTA vascular parameters were reduced in VHL eyes with or without RH versus controls, with significative difference for Vessel Diameter Index. The same OCTA parameters did not significantly differ between VHL eyes with or without RH. In VHL eyes without RH, pRNFL thinning may be the consequence of impaired perfusion of the radial peripapillary capillary plexus, while the increase of pRNFL thickness in VHL eyes with RH may depend on possible activation and proliferation of the other RNFL resident cells, the glial cells.