Advanced glycation end-products and skin autofluorescence in end-stage renal disease: a review.

Chronic kidney disease (CKD), especially in its end stage, is marked by extremely high cardiovascular rates of morbidity and mortality; hemodialysis patients have a five-fold shorter life expectancy than healthy subjects of the same age. In CKD the metabolic products that accumulate in the body are so-called uremic toxins. These include advanced glycation end-products (AGE). AGE levels are markedly increased in CKD patients not only because of impaired excretion but also because of increased production. AGE formation has initially been described as a non-enzymatic reaction between proteins and glucose in the so-called Maillard reaction, but they are also more rapidly formed during oxidative stress and subsequent formation of reactive carbonyl compounds like (methyl)glyoxal. AGE accumulate in tissue where they cross-link with proteins, e.g., collagen, inducing tissue stiffening of blood vessels and skin. They may also interact with receptor of AGE (RAGE) and other receptors, which lead to activation of intracellular transduction mechanisms resulting in cytokine release and further tissue damage in CKD. The accumulation of AGE in the skin can be measured non-invasively using autofluorescence. The skin autofluorescence is a strong marker of cardiovascular mortality in CKD. The focus of this review is on the role of tissue and plasma AGE, and of skin autofluorescence as a proxy of tissue AGE accumulation, in the increase in cardiovascular disease in end stage renal disease (ESRD). This review will also present the possibility of reducing the AGE accumulation in ESRD patients using the following five methods: 1) use of low AGE peritoneal dialysis solutions; 2) use of advanced hemodialysis techniques; 3) use of AGE reducing drugs; 4) optimizing the nutrition of hemodialysis patients; and 5) renal transplantation.

Skin and plasma autofluorescence during hemodialysis: a pilot study.

Skin autofluorescence (AF) is related to the accumulation of advanced glycation end products (AGEs) and is one of the strongest prognostic markers of mortality in hemodialysis (HD) patients. The aim of this pilot study was to investigate whether changes in skin AF appear after a single HD session and if they might be related to changes in plasma AF. Skin and plasma AF were measured before and after HD in 35 patients on maintenance HD therapy (nine women and 26 men, median age 68 years, range 33-83). Median dialysis time was 4 h (range 3-5.5). Skin AF was measured noninvasively with an AGE Reader, and plasma AF was measured before and after HD at 460 nm after excitation at 370 nm. The HD patients had on average a 65% higher skin AF value than age-matched healthy persons (P < 0.001). Plasma AF was reduced by 14% (P < 0.001), whereas skin AF was not changed after a single HD treatment. No significant influence of the reduced plasma AF on skin AF levels was found. This suggests that the measurement of skin AF can be performed during the whole dialysis period and is not directly influenced by the changes in plasma AF during HD.

Flush at room temperature followed by storage on ice creates the best lung graft preservation in rats.

Current clinical lung preservation techniques have not eliminated ischaemia-reperfusion (I/R) injury, despite many improvements. The optimal combination of flush and storage temperatures remain unclear in lung preservation. This is the first study to investigate a range of temperatures with 24-h inflated storage using consistent state-of-the-art preservation techniques. A rat lung transplant model was used to investigate the optimal combination of flush and storage temperatures. In six groups, rat lungs were flushed at 4 °C, 10 °C or room temperature (F(4) /F(10) /F(Rt)) with Perfadex and stored inflated for 24 h in Perfadex on melting ice or at 10 °C (S(ice) /S(10)). Left donor lungs were transplanted for analysis. During 2-h reperfusion, the lung graft function was measured (blood gases, maximum ventilation pressure and static compliance) and lung graft injury was also assessed (W/D ratio, total lung protein, Tryptase, Myeloperoxidase). Right donor lungs were assessed for W/D ratio only after flush and storage. For baseline measurements, left lungs without intervention were used. The combination of F(Rt) -S(ice) showed a significantly higher pO(2), lower P(max), low W/D ratios and total protein levels of left lungs after reperfusion when compared with F(4) -S(ice) and baseline. Storage at 10 °C did not improve preservation. We conclude that F(Rt) -S(ice) creates the best lung graft preservation.

In situ lung perfusion is a valuable tool to assess lungs from donation after circulatory death donors category I-II.

Donations after circulatory death (DCD) lung grafts are an alternative to extend the donor pool in lung transplantation. This study investigates the use of an in situ lung perfusion system (ISLP) in the donor to evaluate category I-II lungs. Pigs were sacrificed by ventricular fibrillation. All animals underwent 20 min of cardiopulmonary resuscitation and 5 min hands-off period after which heparin was administered. In group [WI-1], this was followed by 1 h of warm ischemia (WI) and 2 h of topical cooling (TC). In group [WI-2], 2 h of WI was followed by 1 h of TC. In group [WI-0], there was a minimal period of WI and no TC. In all three groups, the lungs were then evaluated during 60 min with ISLP. [WI-0] lungs showed a significantly higher compliance and Δ PO2 /FiO2 compared with [WI-1] and [WI-2]. PaCO2 and lactate production were higher in [WI-2] versus [WI-0]. Wet/Dry weight ratio was significantly higher in [WI-2] compared with [WI-0] in two lung biopsy locations. A high W/D weight ratio was correlated with a lower compliance, higher lactate production, and a higher PaCO2 . ISLP is an effective way to assess the quality of lungs from category I-II DCD donors.

Increase in skin autofluorescence and release of heart-type fatty acid binding protein in plasma predicts mortality of hemodialysis patients.

Advanced glycation end-products (AGEs) are uremic toxins that accumulate progressively in hemodialysis (HD) patients. The aim of this study was to assess the 1-year increase in skin autofluorescence (ΔAF), a measure of AGEs accumulation and plasma markers, as predictors of mortality in HD patients. One hundred sixty-nine HD patients were enrolled in this study. Skin autofluorescence was measured twice, 1 year apart using an AGE Reader (DiagnOptics Technologies BV, Groningen, The Netherlands). Besides routine blood chemistry, additional plasma markers including superoxide dismutase, myeloperoxydase, intercellular adhesion molecule 1 (ICAM-1), C-reactive protein (hs-CRP), heart-type fatty acid binding protein (H-FABP), and von Willebrand factor were measured at baseline. The mortality of HD patients was followed for 36 months. Skin autofluorescence values of the HD patients at the two time points were significantly higher (P < 0.001) than those of healthy subjects of the same age. Mean 1-year ΔAF of HD patients was 0.16 ± 0.06, which was around seven- to ninefold higher than 1-year ΔAF in healthy subjects. Multivariate Cox regression showed that age, hypertension, 1-year ΔAF, hs-CRP, ICAM-1, and H-FABP were independent predictors of overall mortality. Hypertension, 1-year ΔAF, hs-CRP, and H-FABP were also independent predictors of cardiovascular mortality. One-year ΔAF and plasma H-FABP, used separately and in combination, are strong predictors of overall and cardiovascular mortality in HD patients.

Clinical effectiveness of centrifugal pump to produce pulsatile flow during cardiopulmonary bypass in patients undergoing cardiac surgery.

Although the centrifugal pump has been widely used as a nonpulsatile pump for cardiopulmonary bypass (CPB), little is known about its performance as a pulsatile pump for CPB, especially on its efficacy in producing hemodynamic energy and its clinical effectiveness. We performed a study to evaluate whether the Rotaflow centrifugal pump produces effective pulsatile flow during CPB and whether the pulsatile flow in this setting is clinically effective in adult patients undergoing cardiac surgery. Thirty-two patients undergoing CPB for elective coronary artery bypass grafting were randomly allocated to a pulsatile perfusion group (n = 16) or a nonpulsatile perfusion group (n = 16). All patients were perfused with the Rotaflow centrifugal pump. In the pulsatile group, the centrifugal pump was adjusted to the pulsatile mode (60 cycles/min) during aortic cross-clamping, whereas in the nonpulsatile group, the pump was kept in its nonpulsatile mode during the same period of time. Compared with the nonpulsatile group, the pulsatile group had a higher pulse pressure (P < 0.01) and a fraction higher energy equivalent pressure (EEP, P = 0.058). The net gain of pulsatile flow, represented by the surplus hemodynamic energy (SHE), was found much higher in the CPB circuit than in patients (P < 0.01). Clinically, there was no difference between the pulsatile and nonpulsatile groups with regard to postoperative acute kidney injury, endothelial activation, or inflammatory response. Postoperative organ function and the duration of hospital stay were similar in the two patient groups. In conclusion, pulsatile CPB with the Rotaflow centrifugal pump is associated with a small gain of EEP and SHE, which does not seem to be clinically effective in adult cardiac surgical patients.

Skin color independent assessment of aging using skin autofluorescence.

Skin autofluorescence (AF) for the non-invasive assessment of the amount of accumulated tissue Advanced Glycation Endproducts (AGEs) increases with aging. In subjects with darker skin colors, measurements typically result in lower AF values than in subjects with fair skin colors, e.g. due to selective absorption by skin compounds. Our aim was to provide a new method for calculating skin AF, yielding values that are independent of skin color. The deviation of skin AF of healthy subjects with various darker skin types (N = 99) compared to reference values from Caucasians showed to be a function of various parameters that were derived from reflectance and emission spectra in the UV and visible range (adjusted R(2) = 80%). Validation of the new algorithm, based on these findings, in a separate dataset (N = 141) showed that results of skin AF can now be obtained to assess skin AGEs independently of skin color.

The effects of cryopreservation on red blood cell rheologic properties.

BACKGROUND: In transfusion medicine, frozen red blood cells (RBCs) are an alternative for liquid-stored RBCs. Little is known about the rheologic properties (i.e., aggregability and deformability) of thawed RBCs. In this study the rheologic properties of high-glycerol frozen RBCs and postthaw stored in saline-adenine-glucose-mannitol medium were compared to those of conventionally liquid-stored and fresh RBCs. STUDY DESIGN AND METHODS: Fresh RBCs were obtained from healthy volunteers. Leukoreduced liquid-stored and thawed deglycerolized RBC units were obtained from the Sanquin Blood Bank. RBCs were tested for aggregability (aggregation index [AI]), deformability (elongation index [EI]), and various hematologic variables. RESULTS: The AI of thawed RBCs was reduced, compared to fresh and liquid-stored RBCs (p<0.05). The EI of stored RBCs was significantly enhanced over a shear stress range of 2.0 to 50Pa compared to fresh RBCs (p<0.05). No significant differences in EI between thawed and 21- or 35-day liquid-stored RBCs were observed. The osmotic fragility, hemolysis, mean cell volume, and mean cell hemoglobin concentration of thawed RBCs were markedly altered, compared to fresh and liquid-stored RBCs (p< 0.05). The adenosine triphosphate (ATP) content of thawed RBCs was similar to 3- or 21-day liquid-stored and fresh RBCs. CONCLUSIONS: Thawed RBCs are more fragile than conventionally liquid-stored and fresh RBC. The freeze-thaw-wash process, however, did not adversely affect the aggregability and deformability or the ATP content of thawed RBCs. Based on the rheologic properties, cryopreserved RBCs are a valuable alternative to liquid-stored RBCs.

Is red blood cell rheology preserved during routine blood bank storage?

BACKGROUND: Red blood cell (RBC) units stored for more than 2 weeks at 4 degrees C are currently considered of impaired quality. This opinion has primarily been based on altered RBC rheologic properties (i.e., enhanced aggregability, reduced deformability, and elevated endothelial cell interaction), during prolonged storage of nonleukoreduced RBC units. In this study, the rheologic properties and cell variables of leukoreduced RBC units, during routine blood bank storage in saline-adenine-glucose-mannitol, were investigated. STUDY DESIGN AND METHODS: Ten leukoreduced RBC units were stored at the blood bank for 7 weeks at 4 degrees C. RBCs were tested weekly for aggregability, deformability, and other relevant variables. RESULTS: RBC aggregability was significantly reduced after the first week of storage but recovered during the following weeks. After 7 weeks aggregability was slightly, but significantly, reduced (46.9 + or - 2.4-44.3 + or - 2.2 aggregation index). During storage the osmotic fragility was not significantly enhanced (0.47 + or - 0.01% phosphate-buffered saline) and the deformability at shear stress of 3.9 Pa was not significantly reduced (0.36 + or - 0.01 elongation index [EI]). The deformability at 50 Pa was reduced (0.58 + or - 0.01-0.54 + or - 0.01 EI) but remained within reference values (0.53 + or - 0.04). During 5 weeks of storage, adenosine triphosphate was reduced by 54% whereas mean cell volume, pH, and mean cell hemoglobin concentration were minimally affected. CONCLUSIONS: RBC biochemical and physical alterations during storage minimally affected the RBC ability to aggregate and deform, even after prolonged storage. The rheologic properties of leukoreduced RBC units were well preserved during 7 weeks of routine blood bank storage.

Does hepatitis C increase the accumulation of advanced glycation end products in haemodialysis patients?

BACKGROUND: Hepatitis C may cause increased levels of oxidative stress that contribute to accumulation of advanced glycation end products (AGEs), which increase the risk of cardiovascular disease (CVD). The aim of this study was to determine the influence of hepatitis C on AGE accumulation in haemodialysis patients. METHODS: AGE accumulation was measured by means of skin autofluorescence (AF) in 92 haemodialysis (HD) patients and 93 age-matched healthy controls. In the HD patients, CVD-related biochemical variables were also measured. The HD patients were tested for hepatitis C virus (HCV) antibodies and allocated to a HCV+ or HCV- group. RESULTS: Skin AF of the healthy subjects was lower than skin AF in the HD patients (3.13 +/- 0.95 vs 2.2 +/- 0.47; P < 0.001). We calculated the average increase of skin AF in the healthy subjects to be 0.017 arbitrary units per year, being 14 times lower than in HD patients with CVD only and 20 times lower than in HD patients suffering from combined CVD and diabetes mellitus (DM). Multivariate regression analysis showed that AGE accumulation in HD patients can be described by the independent effects of age, DM, CVD and HD vintage. Although inter-cellular adhesion molecule 1 and liver enzymes were elevated in HCV+ HD patients, levels of oxidative stress markers and skin AF were not significantly different between HCV+ and HCV- HD patients. CONCLUSIONS: AGE accumulation was higher in the HD patients than in the healthy controls. AGE accumulation did not differ in HCV+ and HCV- HD patients. This might be due to the fact that hepatitis C did not cause oxidative stress in our HD population. Independent markers of AGE accumulation were age, HD vintage, DM and CVD, but not hepatitis C.

Time development models for perfusion provocations studied with laser-Doppler flowmetry, applied to iontophoresis and PORH.

OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Abnormal endothelium-dependent microvascular dilator reactivity in pregnancies complicated by normotensive intrauterine growth restriction.

OBJECTIVE: Normotensive intrauterine growth restriction and preeclampsia share a similar placenta pathophysiology, whereas maternal clinical manifestations differ. Clinical symptoms of preeclampsia are partly attributed to vascular endothelial dysfunction, but it is unclear whether this phenomenon plays a role in intrauterine growth restriction. Therefore, we investigated microvascular endothelial function in women with intrauterine growth restriction. STUDY DESIGN: Laser Doppler fluxmetry was used combined with iontophoresis of acetylcholine and sodium nitroprusside, namely, endothelium-dependent and endothelium-independent vasodilators. We studied 12 women with intrauterine growth restriction and 16 controls in the third trimester of pregnancy. All women had prepregnancy body mass indexes < 26. RESULTS: Acetylcholine-mediated vasodilatation was significantly increased in women with intrauterine growth restriction compared with controls (743% +/- 120% vs 390% +/- 67%, P = .01); sodium nitroprusside-mediated vasodilatation was not different (360% +/- 55% vs 363% +/- 65%, P > .99). CONCLUSION: Nonobese women with normotensive intrauterine growth restriction show abnormal endothelium-dependent microvascular vasodilatation, suggesting endothelial dysfunction as in preeclampsia. Obviously, for the clinical manifestation of preeclampsia additional factors are required, and a role of metabolic syndrome and obesity has been suggested.

Depth-kymography of vocal fold vibrations: part II. Simulations and direct comparisons with 3D profile measurements.

We report novel direct quantitative comparisons between 3D profiling measurements and simulations of human vocal fold vibrations. Until now, in human vocal folds research, only imaging in a horizontal plane was possible. However, for the investigation of several diseases, depth information is needed, especially when the two folds act differently, e.g. in the case of tumour growth. Recently, with our novel depth-kymographic laryngoscope, we obtained calibrated data about the horizontal and vertical positions of the visible surface of the vibrating vocal folds. In order to find relations with physical parameters such as elasticity and damping constants, we numerically simulated the horizontal and vertical positions and movements of the human vocal folds while vibrating and investigated the effect of varying several parameters on the characteristics of the phonation: the masses and their dimensions, the respective forces and pressures, and the details of the vocal tract compartments. Direct one-to-one comparison with measured 3D positions presents-for the first time-a direct means of validation of these calculations. This may start a new field in vocal folds research.

Early events in kidney donation: progression of endothelial activation, oxidative stress and tubular injury after brain death.

Cerebral injury leading to brain death (BD) causes major physiologic derangements in potential organ donors, which may result in vascular-endothelial activation and affect posttransplant graft function. We investigated the kinetic of pro-coagulatory and pro-inflammatory endothelial activation and the subsequent oxidative stress and renal tubular injury, early after BD declaration. BD was induced by slowly inflating a balloon-catheter inserted in the extradural space over a period of 30 min. Rats (n = 30) were sacrificed 0.5, 1, 2 or 4 h after BD-induction and compared with sham-controls. This study demonstrates immediate pro-coagulatory and pro-inflammatory activation of vascular endothelium after BD in kidney donor rats, proportional with the duration of BD. E- and P-Selectins, Aalpha/Bbeta-fibrinogen mRNA were abruptly and progressively up-regulated from 0.5 h BD onwards; P-Selectin membrane protein expression was increased; fibrinogen was primarily visualized in the peritubular capillaries. Plasma von Willebrand factor was significantly higher after 2 h and 4 h BD. Urine heart-fatty-acid-binding-protein and N-acetyl-glucosaminidase, used as new specific and sensitive markers of proximal and distal tubular damage, were found significantly increased after 0.5 h, with a maximum at 4 h. Unexpectedly, oxidative stress was detectable only late, after the installation of tubular injury, suggesting only a secondary role for hypoxia in triggering these injuries.

New laryngoscope for quantitative high-speed imaging of human vocal folds vibration in the horizontal and vertical direction.

We report the design of a novel laser line-triangulation laryngoscope for the quantitative visualization of the three-dimensional movements of human vocal folds during phonation. This is the first successful in vivo recording of the three-dimensional movements of human vocal folds in absolute values. Triangulation images of the vocal folds are recorded at the rate of 4000 fps with a resolution of 256x256 pixels. A special image-processing algorithm is developed to precisely follow the subpixel movements of the laser line image. Vibration profiles in both horizontal and vertical directions are calibrated and measured in absolute SI units with a resolution of +/-50 microm. We also present a movie showing the vocal folds dynamics in vertical cross section.

Depth-kymography: high-speed calibrated 3D imaging of human vocal fold vibration dynamics.

We designed and developed a laser line-triangulation endoscope compatible with any standard high-speed camera for a complete three-dimensional profiling of human vocal fold vibration dynamics. With this novel device we are able to measure absolute values of vertical and horizontal vibration amplitudes, length and width of vocal folds as well as the opening and closing velocities from a single in vivo measurement. We have studied, for the first time, the generation and propagation of mucosal waves by locating the position of its maximum vertical position and the propagation velocity. Precise knowledge about the absolute dimensions of human vocal folds and their vibration parameters has significant importance in clinical diagnosis and treatment as well as in fundamental research in voice. The new device can be used to investigate different kinds of pathological conditions including periodic or aperiodic vibrations. Consequently, the new device has significant importance in investigating vocal fold paralysis and in phonosurgical applications.

Prevention of pin tract infection in external stainless steel fixator frames using electric current in a goat model.

Pin tract infections of external fixators used in orthopaedic reconstructive bone surgery are serious complications that can eventually lead to periostitis and osteomyelitis. In vitro experiments have demonstrated that bacteria adhering to stainless steel in a biofilm mode of growth detach under the influence of small electric currents, while remaining bacteria become less viable upon current application. Therefore, we have investigated whether a 100microA electric current can prevent signs of clinical infection around percutaneous pins, implanted in the tibia of goats. Three pins were inserted into the lateral right tibia of nine goats, of which one served for additional frame support. Two pins were infected with a Staphylococcus epidermidis strain of which one pin was subjected to electric current, while the other pin was used as control. Pin sites were examined daily. The wound electrical resistance decreased with worsening of the infection from a dry condition to a purulent stage. After 21 days, animals were sacrificed and the pins taken out. Infection developed in 89% of the control pin sites, whereas only 11% of the pin sites in the current group showed infection. These results show that infection of percutaneous pin sites of external fixators in reconstructive bone surgery can be prevented by the application of a small DC electric current.

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.

Histological assessment of titanium and polypropylene fiber mesh implantation with and without fibrin tissue glue.

Polypropylene (PP) and titanium (Ti) meshes are well-known surgical implants that provoke a relative low foreign body reaction. Firm stabilization of the implant is important to prevent migration and subsequent failure of the operation. Fibrin tissue glues are commercially available adhesives and are widely accepted and applied in the medical field for hemorrhage, surgical bleeding, support of wound healing, wound and tissue gluing, sealing, and closure but also as antiadhesive agent in certain applications. The objective of this study was to evaluate the additional histological effect of fibrin glue application combined with two different types of meshes. Six pieces of mesh of each were subcutaneously implanted for 3, 6, and 12 weeks, with and without fibrin glue. After excision, processing, and staining, light microscopic analysis was performed on the sections, using subjective histological description and histomorphometry. Capsule quality, capsule thickness, interstitial quality, and total score were evaluated. To compare the samples with glue and without glue, analysis of variance (ANOVA) tests were carried out. No complications were observed. In general, the glue remnants remained visible at 3 and 6 weeks of implantation, accompanied by an inflammatory reaction and macrophage activity. At 12 weeks, all samples showed good tissue integration without evidence of glue. Evidently, the samples with glue demonstrated a prolonged inflammatory response and were surrounded by fibrous tissue capsules that were significantly thicker compared with the samples without glue (p < 0.05).