Experimental investigations on graphene oxide/rubber composite thermal conductivity.

Graphene oxide/rubber composites were experimentally investigated for obtaining their thermal properties. Three kinds of the composite matrix material have been used: NBR, HNBR and FKM. The reduced graphene oxide in the form of crumped flakes has been applied as the filler influencing on thermal conductivity of the composites. Two values of graphene oxide weight concentration have been taken into account in the investigation. Thermal conductivity of the composites and basic matrix has been measured by the professional apparatus with the use of the guarded heat plate method. Before measurements the preliminary tests using the simplified comparative method have been performed. The results obtained, both from preliminary tests and using the guarded heat plate method, show an increase in thermal conductivity with increasing the reduced graphene oxide content in the composite. The experimental investigation allowed to determine not only the increase in thermal properties of graphene oxide/rubber composites compared to the basic matrix, but also the absolute values of thermal conductivities. Additionally, the SEM analysis showed that the tested composite samples contain agglomerates of the rGO nanoparticles. The occurrence of agglomerates could affect the composite thermal properties. This was noticed in the comparatively measurements of the temperature of different composites during the heating of samples tested. The maximum enhancement of thermal conductivity obtained was about 11% compared to the basis matrix of the composites tested.

Carboxylated and intact osteocalcin predict adiponectin concentration in hemodialyzed patients.

Purpose Disrupted bone metabolism in patients with chronic kidney disease (CKD) is associated with elevated concentrations of biochemical bone markers. Recently, animal studies show the role of osteocalcin in energy metabolism, which is partially confirmed in humans. The aim of our study was to evaluate the relationships between serum concentrations of bone markers and indices of energy metabolism in CKD patients on maintenance hemodialysis; in particular, the relationship between various forms of osteocalcin and adiponectin. Patients and methods The cross-sectional study included 155 hemodialyzed stage 5 CKD patients. Serum concentrations of glucose, insulin, adiponectin, bone alkaline phosphatase (bALP), tartrate resistant acid phosphatase (TRAP), carboxylated (cOC), undercarboxylated (ucOC), and intact osteocalcin (OC) were determined. Results In total cohort, bALP, TRAP, cOC, and ucOC negatively correlated with BMI. All analyzed bone markers positively correlated with adiponectin in total cohort and in men. In multiple linear regression analysis including all patients, log(cOC) and log(intact OC) were the only bone markers that predicted log(adiponectin) (beta = 0.22; p = 0.016 and beta = 0.26; p = 0.010) independently of sex, dialysis vintage, CRP, insulin, iPTH concentrations, BMI, and age. Conclusions Our data confirm the positive association between cOC, intact OC, and adiponectin concentrations in CKD patients on maintenance hemodialysis.

Relationship between fetuin-A, bone turnover and inflammatory markers concentrations in serum of maintenance hemodialyzed patients.

Introduction: Fetuin-A plays an important role in bone turnover and vascular calcification. Aim: The aim of the study was to assess the relationship between serum fetuin-A concentrations, inflammatory and bone turnover markers of patients on maintenance hemodialysis. Materials and Methods: The study was performed in 71 patients (21 women, 40 men) aged 60 ± 12 years on chronic dialysis because of end-stage renal failure for a period of 75 ± 57.2 months. The routine laboratory tests were performed with Modular P analyzer (Roche Diagnostics), serum concentrations of iPTH were measured using Nichols method, hsCRP and IL-6 using nephelometric techniques while fetuin-A, bone-specific alkaline phosphatase (bALP), fully carboxylated osteocalcin (cOC), undercarboxylated osteocalcin (ucOC), and fibroblast growth factor-23 (FGF-23) were measured using commercially available ELISA kits. Results: Concentrations of fetuin-A were significantly positively correlated with albumin (r=0.37, p=0.003) and negatively associated with patients age (r=26, p=0.04), log (iPTH) (r=0.31, p=0.02), log (CRP) (r=0.31, p=0.02), log (IL-6) (r=0.41, p=0.001), log (ucOC) (r=-0.29, p=0.02), and log (FGF-23) (r=0.27, p=0.04). Conclusions: 1. Patients on maintenance hemodialysis suffer from severe disturbances of bone turnover. 2. Low serum fetuin-A levels are associated with increase markers of bone turnover and inflammation.

[Cardiovascular calcification and five-years mortality in patients on maintenance hemodialysis]. / Zwapnienia w ukladzie sercowo-naczyniowym a 5-letnia smiertelnosc pacjentów leczonych powtarzanymi hemodializami.

The very high cardiovascular mortality and morbidity in hemodialyzed patients (HD) is strongly associated with cardiovascular calcification. The aim of the study was to find the predictors of mortality in HD patients during 5-years observation period. The study group was composed of 64 patients (35 F, 29 M) aged 25-75 years (mean 48.9) hemodialyzed three times a week for 12-275 months (mean 77.8). The levels of hemoglobin, total protein, albumin, Ca, P, Ca x P, iPTH, cholesterol, triglycerides, fibrinogen, insulin, homocysteine, leptin, procalcitonin, CRP, IL-6, TGF-beta, PDGF were assessed and all patients underwent Calcium Score (CS) of coronary arteries (CACS) calculation using MSCT and B-mode ultrasound of carotid arteries for intima-media thickness (CCA-IMT), as well as echocardiographic assessment with LVMI calculation and heart valves evaluation at the start of observation. The self-elaborated Cumulative Calcification Index (CCl) was calculated as a sum of CACS Index according to Rumberger et al. (CS<10-0, 10400 - 3 points); number of calcified plaques in carotid arteries (0-0, 1 - 1, 2 - 2, 3 and more - 3 points) and the number of calcified heart valves. At the start of the study the median value of CCl was 4 and interquartile range 4. Only 2 (3%) patients were free of any type of cardiovascular calcification (CCl =0), 15 (23%) patients had minimal calcification (CCl 1 to 2 points), 33 (52%) average (2 - 6 points) and 14 (22%) patients had severe calcification (CCl>6). 21 (32,8%) patients died during observation period. Patients who died were older (56.9 vs. 45.3 yrs.) and had higher CS at the start (1275 vs. 356), higher CCA-IMT (0.948 vs. 0.687 mm) and CCl (6.15 vs. 3.63) values. Those patients had also higher CRP (0.645 vs. 0.245 mg/dl) and IL-6 (10.16 vs. 4.15 pg/ml) levels (p<0.05). LVMI and mean: hemoglobin, total protein, albumin, Ca, P, Ca x P, iPTH, cholesterol, triglycerides, fibrinogen, insulin, homocysteine, leptin, procalcitonin, TGF-beta as well as PDGF levels did not differ between the groups. In logistic regression model (p<0.00002), among tested parameters only CCl was an independent and statistically significant factor of mortality with OR=1.82 per every point of CCl (p<0.0003). Cardiovascular calcification expressed as CCl confirmed to be a strong predictor of mortality in HD patients.

[Influence of microinflammation and oxidative stress on atherosclerosis progression and calcifications in cardiovascular system of hemodialyzed patients during two years follow-up]. / Wplyw mikrozapalenia i stresu oksydacyjnego na progresje miazdzycy i zwapnien w ukladzie krazenia u chorych hemodializowanych w okresie dwuletniej obserwacji.

Atherosclerosis and calcifications in the cardio-vascular system are the most frequent causes of increased morbidity and mortality in patients with end-stage renal disease treated with hemodialyses. The aim of this study was to estimate the atherosclerosis progression and presence of calcifications in the circulatory system in patients treated with hemodialyses using, non-invasive imaging diagnostic techniques and to search for the relationships between these changes and microinflammation and oxidative stress during two years. The study was performed in 73 patients (36 female and 37 male), aged 25 to 75 years (mean -49.5), treated with hemodialyses, 3 times/week for 12 to 275 months (mean -73.8). In each patient before starting hemodialysis levels of: ox-LDL, Lp (a), procalcitonin, IL-1beta, IL-6, CRP, TGFbeta, TNFalpha, PDGF, AOPP and MPO were determined. Presence of artery calcifications was detected by Multi-Row Spiral Computed Tomography (MSCT) and expressed as coronary artery calcification score (CACS). Ultrasonography was used to evaluate CCA-IMT. During the study CACS increased significantly after 12 and 24 months (p < 0.00001) as compare with baseline. After 12 months, CACS increase significantly correlated with procalcitonin level (r = 0.30 p = 0.01) and after 24 months with CRP (r = 0.46; p = 0.0002) and IL-6 (r = 0.36; p = 0.005). Independent factor of coronary artery calcification progression after 24 months of observation was only CRP (beta = 0.569). CCA-IMT increased during the study and this increase was statistically significant (p < 0.00001). CCA-IMT increase correlated with CACS growth after 12 (r = 0.36; p = 0.003) and 24 months (r = 0.39; p = 0.002). After 12 months significant relationship was noted with procalcitonin (r = 0.29; p = 0.022). After 24 months CCA-IMT correlated with AOPP (r = -0.30; p = 0.017). The independent factor of CCA-IMT progression after 24 months of observation was only CACS (delta CACS beta = 0.49). From the performed study, we can conclude that exacerbation of atherosclerosis and calcification in the circulatory system of patients treated with maintenance hemodialyses depends on microinflammation and oxidative stress. Reasonable tools for diagnostic algorithm estimation of atherosclerosis advancement in this group of patients are non-invasive, visual diagnostic techniques such as MSCT and ultrasonography.

Factors involved in vascular calcification and atherosclerosis in maintenance haemodialysis patients.

BACKGROUND: Atherosclerosis and vascular calcifications are common causes of morbidity and mortality in maintenance haemodialysis patients. In addition to the well-known traditional risk factors, uraemia-specific factors appear to enhance dramatically the progression of the pathological processes involved. The aim of the present study was to evaluate the degree of atherosclerosis and vascular calcifications in chronic haemodialysis patients using non-invasive imaging methods, and to identify potentially involved factors. METHODS: The study included 73 patients (36 females, 37 males), aged 25-75 years, who were on haemodialysis treatment for 12-275 months (mean dialysis vintage 73.8 months). We assessed the following circulating parameters: calcium (Ca), phosphorus, 'intact' parathyroid hormone (iPTH), 25OH vitamin D, lipids, oxidized LDL (ox-LDL), Lp(a), homocysteine, leptin, IL-1-beta, IL-6, CRP, TGF-beta, TNF-alpha, (PDGF), advanced oxidation protein products (AOPP) and myeloperoxidase activity (MPO). Coronary artery calcification score (CACS) was assessed using multi-row spiral CT (MSCT). Intima-media thickness index of the common carotid artery (CCA-IMT) and presence of cervical artery atherosclerotic plaques were evaluated by ultrasonography. RESULTS: Coronary artery calcifications were observed in 79.5% of the patients, with CACS ranging from 0 to 4987. In univariate analysis, a positive correlation was observed between CACS and age, BMI, iPTH, CRP, IL-6 and CCA-IMT, whereas an inverse correlation existed with 25OH vitamin D, TGF-beta and PDGF. CCA-IMT ranged from 0.4 to 1.1 mm. It was positively correlated, in univariate analysis, with age, CACS, CRP and Il-6, and negatively with 25OH vitamin D, TGF-beta and PDGF. Only CACS remained as independent predictive factor of CCA-IMT in multivariate analysis. Atherosclerotic plaques were found in the carotid arteries of 53 patients (72%). The number of plaques was positively correlated with age, CACS, phosphorus, MPO, CRP and IL-6, and inversely with 25OH vitamin D in univariate analysis. In multivariate regression analysis, only age and CACS remained as independent variables. CONCLUSION: In addition to classic risk factors, the degree of atherosclerosis and vascular calcification in our dialysis patient population were associated with several factors that are frequently abnormal in advanced chronic renal failure, but except age, all of them were interdependent. Notably, as in the general population, CACS was an independent predictor of the degree of atherosclerosis in haemodialysis patients.

[Evaluation of atherosclerosis progression in patients treated repeatedly with hemodialysis]. / Ocena stopnia rozwoju miazdzycy u chorych leczonych powtarzanymi hemodializami.

The main cause of increased morbidity and mortality in patients on maintenance hemodialysis are cardiovascular complications due to accelerated atherosclerosis. Lipid profile disturbances, increased levels of homocysteine (HC), fibrinogen, iPTH as and Ca-P abnormalities seem to be the important factors in atherosclerosis progression. The aim of the study was to evaluate the advancement of atherosclerosis in patients on maintenance hemodialysis and to assess levels of pro-atherosclerotic factors. The study included 50 patients (30 M, 20 F) aged 21-75 years (mean 48.6 y) hemodialyzed three times a week for 12 to 282 months (mean 114.5 m). The homocysteine, fibrinogen, iPTH, calcium, phosphate and indices of lipid metabolism such as total cholesterol, HDL, LDL, triglicerides, Lp (a) and Apo B were measured before hemodialysis. To evaluate the advancement of atherosclerosis, all patients underwent MSCT using Somatom plus 4 apparatus with calcium scoring (CS) calculation and B-mode ultrasound for IMT using Acuson 128 XP 10 apparatus. The above applied methods helped to evaluate changes in central and peripheral arteries. In CS testing, coronary artery calcifications were present in 36 patients (72%). The CS ranged from 0 to 4345, with the mean CS being 584 (SD = 1012). The CS correlated significantly with age (r = 0.39; p < 0.005), P (r = 0.33; p < 0.05), CaxP product (r = 0.39; p < 0.05), iPTH (r = 0.43; p < 0.001) and with IMT (r = 0.56; p < 0.0001). The IMT ranged from 0.5 to 1.5, with mean of 0.89 (SD = 0.28). The IMT correlated significantly with age (r = 0.54; p < 0.0001), time on dialysis (r = 0.40; p < 0.01), fibrinogen (r = 0.43; p < 0.02), LDL (r = 0.30; p < 0.05), P (r = 0.29; p < 0.05), and CaxP product (r = 0.3; p < 0.05). Based on our study, we conclude that age, time on dialysis, increased levels of homocysteine, LDL cholesterol, fibrinogen, P, and iPTH as well as Ca-P disturbances are strong predictors of atherosclerosis in HD patients.

[Hyperhomocysteinemia and advancement of atherosclerosis in patients with chronic renal failure on maintenance hemodialysis]. / Hiperhomocysteinemia a zaawansowanie miazdzycy tetnic u chorych z przewlekla niewydolnoscia nerek leczonych hemodializami.

Cardiovascular diseases connected with atherosclerosis are the main factor of morbidity and mortality in patients with end-stage renal failure. Hyperhomocysteinemia is a known and independent risk factor of atherosclerosis, occurring in 85-95% patients treated with hemodialysis. The aim of this study was to analyse relation between plasma level of homocysteine and chosen indicators of atherosclerosis development and also examined retrospectively cardiovascular complications in these patients. The study was carried out in 100 patients on hemodialysis who were divided into two groups: 72 patients with mild (20.74 mumol/l +/- 3.75) and 28 patients with moderate hyperhomocysteinemia (38.81 mumol/l +/- 9.81). Ultrasonographic examinations of Carotid Communis Artery Intima-Media Thickness (IMT), Ankle-Arm Blood Pressure Index (AABPI), echocardiographic parameters and biochemical examinations such as: PTH, folic acid and Vitamin B12, total protein, albumin, fibrinogen, glucose, total, LDL and HDL cholesterol, transferring, apolipoprotein B, lipoprotein (a), sodium potassium, calcium, phosphate, magnesium, iron, ferritin, urea, creatinine, uric acid and value of Hb, Ht, total iron binding capacity and transferring saturation, were performed. Patients with hypertension were divided into groups according to the number of taken anti-hypertensive drugs. Hyperhomocysteinemia was confirmed in 96% of patients. Frequency and type of acute cardiovascular complications were not related with the level of hyperhomocysteinemia. Statistically significant difference between IMT and level of hyperhomocysteinemia was observed. In patients with mild hyperhomocysteinemia IMT was 0.68 mm +/- 0.24 whereas in patients with moderate hyperhomocysteinemia 0.80 mm +/- 0.25, p < 0.036). Positive correlation between level of homocysteine and IMT (r = 0.22, p < 0.03) was noted. Based on this study, we concluded, that measurement of intima-media thickness is a good indicator of atherosclerosis development and correlates with hyperhomocysteinemia in patients on maintenance hemodialysis. It clearly confirms the role of hyperhomocysteinemia as significant risk factor of atherosclerosis in those patients.