[Blood pressure changes in chronically haemodialysed patients]

BACKGROUND

Poor blood pressure control in chronically haemodialysed patients leads to increased cardiovascular morbidity and mortality. Information on valid values of blood pressure during haemodialysis and out of office is very important in order to set up adequate treatment.

AIM

To measure blood pressure during the haemodialysis and the subsequent 24-hour period using an ambulatory blood pressure monitoring (ABPM) in patients with normal blood pressure (BP) and patients with high normal BP and hypertension. Relationship between time-dependent blood pressure changes, ultrafiltration (UF) and interdialytic weight gain (IDWG) was analysed.

PATIENTS AND METHODS

Fifty chronically haemodialysed (> 3 months) patients (males/females 33/18) aged 57.5 (53-63; median, interquartile interval) years were studied. Systolic and diastolic pressures (SP, DP) were measured during haemodialysis every hour (H0-H4) and over following 24 hours using Spacelab 90217 monitor. Pulse pressure (PP) values were calculated as a difference between SP and DP. The patients were stratified into two groups based on the cut-off-point calculated as the mean of two mean arterial pressure (MAP) values obtained at the beginning and after the first hour of HD: Group A (n = 25), MAP < 100 mm Hg; Group B (n = 25), MAP 100 mm Hg. Interdialytic weight gain was measured before HD (IDWG1) and after the ABPM (IDWG2); also ultrafiltration (UF) was obtained. The post-dialysis 24-h ABPM period was divided into eight 3-hour intervals (M1-8).

RESULTS

During HD no significant change in SP, DP or PP was found in both group, but there was a significant difference (p = 0.01) between both groups in SP, DP and PP. Values of BP at the end of dialysis were in group A: SP 125 (120-130) mm Hg, DP 75 (60-80) mm Hg and PP 50 (40-60) mm Hg in group B: SP 150 (140-160) mm Hg, DP 80 (80-90) mm Hg a PP 60 (60-70) mm Hg. We did not find any influence of IDWG1 or IDWG2 on SP or DP in both groups. Relationship between UF 3 000 (2 500-4 300) ml and SP (Δ sTK -5 mm Hg) was confirmed only in group A (p = 0.04). In group A, we found a decrease in SP during the third and sixth 3-hour interval (p = 0.01; p = 0.02) including sleeping period, all compared to the end of HD (H4). In group B, such a decrease in SP was found only in the second sleep interval (p = 0.01) and in the sixth 3-hour interval (p = 0.03), all compared to the end of HD (H4). As to DP at the end of dialysis (H4) in group A, it differed only in the third 3-hour interval (p = 0.02), but not during the sleeping period. In group B, the decrease of DP compared to the end HD (H4) was recorded during the two sleep intervals (p = 0.01), and also in the sixth and seventh 3-hour intervals (p = 0.01; p = 0.03). In group A, PP was compared to the end of HD (PPH4) significantly decreased in the first 3-hour interval (p = 0.02) and in seventh and eight 3-hour interval (p = 0.03; p = 0.04). In group B, PP did not significant change from the end of HD. Difference in SP between both groups was maintained over the entire course of ABPM (p = 0.01). However, DP values in both groups were different in the first and third 3-hour intervals (p = 0.01) but in following intervals DP in group B decreased to the level of that in group A. There was no significant difference in the proportion of non-dippers and reverse dippers in both groups.

CONCLUSION

Systolic, diastolic, mean arterial and pulse pressure pressures were not significantly changed during the haemodialysis in both groups. Relationship between ultrafiltration and systolic pressure was confirmed only in group A. No influence of interdialytic weight gain on blood pressure during 24 hours was seen in either group. Systolic pressure decreased in both groups during the nighttime compared to post-HD values, but diastolic pressure decreased only in group B. PP did not decrease during the night in any group. There was no significant difference in the proportion of non-dippers and reverse dippers in both groups.

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.

Liver mitochondrial respiratory function and coenzyme Q content in rats on a hypercholesterolemic diet treated with atorvastatin

Statins, inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, are effective drugs in the treatment of hypercholesterolemia, however, their undesirable actions are not fully known. We investigated the effects of atorvastatin on the oxidative phosphorylation and membrane fluidity in liver mitochondria, and also on the coenzyme Q (CoQ) content in the mitochondria, liver tissue, and plasma of rats on a standard (C) and hypercholesterolemic (HCh) diet. Atorvastatin was administered at either low (10 mg kg(-1)) or high dose (80 mg kg(-1)) for four weeks. The high dose of the drug decreased the concentrations of total cholesterol and triacylglycerols in the plasma and liver of rats on a HCh diet. Administration of atorvastatin was associated with decreased oxygen uptake (state 3), and oxidative phosphorylation rate in the mitochondria of both C and HCh rats. Further, the drug influenced mitochondrial membrane fluidity and dose-dependently reduced concentrations of oxidized and reduced forms of CoQ in the mitochondria. Our findings point to an association between in vivo administration of atorvastatin and impaired bioenergetics in the liver mitochondria of rats, regardless of diet, in conjunction with simultaneous depletion of oxidized and reduced CoQ forms from the mitochondria. This fact may play a significant role in the development of statin-induced hepatopathy.

Accurate normalization factor for wire myography of rat femoral artery

Wire myograph is a device for the in vitro investigation of both, active and passive properties of arteries. Arteries from a variety of animal species, pathological states, and vascular beds were investigated using this method. We focus on the normalization procedure which is aimed to standardize experimental settings and, in part, to simulate physiological conditions. During normalization, it is determined the internal circumference of a vessel stretched to a tension that corresponds to the transmural pressure of 100 mm Hg (IC100). Once it is determined, the internal circumference is traditionally set to (0.9 IC100). However, this constant 0.9, called also the normalization factor (NF), was experimentally determined for rat small mesenteric arteries only. Therefore, the aim of our work was to show the influence of different NFs on the passive tension and reactivity of both, rat femoral arteries (FA) and the first branches of superior mesenteric arteries (MA). We found out that the maximal active wall tension of the FA was achieved at the NF value of 1.1, and that of the MA at 0.9. Considering the values of the active wall tension we suggest that higher reactivity and better signal-to-noise ratio in FA can be achieved when the NF is set at least to 1.0.

Predictive validity of MRI in detecting and following cholesteatoma

High recurrence rate of the middle ear cholesteatoma requires regular postoperative follow-up. This study evaluated data from the patients investigated with DW MRI to ascertain (1) the strength of the technique in detecting primary, and residual recurrent cholesteatoma, and (2) its accuracy in differentiating cholesteatoma from postoperative tissue changes. The diagnostic accuracy of two different DW imaging (EPI and non-EPI) techniques was evaluated. The data have been collected prospectively from 33 consecutive patients with either primary cholesteatoma, or with suspicious symptoms for potential cholesteatoma recurrence. The findings from non-EPI (HASTE) DW MR and EPI DW MR images were blindly compared with those obtained during a primary or secondary surgery. Preoperative non-EPI (HASTE) DWI pointed to a cholesteatoma in 25 out of 33 patients. In this subgroup, cholesteatoma were confirmed also by the surgery. In five cases, the non-EPI (HASTE) DWI did not show a cholesteatoma in the temporal bone, which agreed with the surgical findings. Three misclassifications were made by non-EPI (HASTE) DWI, all in the subgroup of patients indicated for primary surgery. The resulting pooled sensitivity of non-EPI (HASTE) DW imaging for diagnosing cholesteatoma in our study amounted to 96.15% (95% confidence interval (CI) 80.36-99.9), specificity was 71.43% (95% CI 29.04-96.33). Positive predictive value was 92.59% (95% CI 75.71-99.09) and negative predictive value 83.33% (95% CI 35.88-99.58). In conclusion, we recommend the non-EPI (HASTE) DW MRI as a valid method for diagnosing cholesteatoma and follow-up after cholesteatoma surgery.

Biophysical investigation on left ventricular myocytes in rats with experimentally induced diabetes

Diabetes is a recognized risk factor of heart disease. The abnormalities related to a decreased heart performance probably arise at cellular and molecular levels already in the asymptomatic phase of diabetes. However, the early alterations initiating a sequence of events that culminates in the clinical signs have not been fully elucidated yet. This review deals with some biophysical methods applied to investigation of left ventricular myocytes in rats with streptozotocin diabetes, as well as our most important findings concerning diabetes-induced cell changes which cannot be captured by other techniques. The observed decrease in sarcolemmal membrane fluidity is causatively associated with increased glycation and glycoxidation. On the other hand, an increase in the mitochondrial membrane fluidity may be attributed to augmented energy transduction through the membranes. We reported for the first time concurrent measurements of membrane potential and dynamics, and respiratory chain activities in rat heart mitochondria, as well as calcium transients in the myocytes from diabetic hearts together with the assessed quantitative relationships among these variables. We were able to detect some significant alterations that may underlie myocyte dysfunction and subsequent remodeling of the heart. We suppose that not all these changes reflect mechanisms leading to pathology; some may represent adaptive and compensatory responses to diabetes.

Mitochondrial function in heart and kidney of spontaneously hypertensive rats: influence of captopril treatment

Effect of captopril treatment on capability of heart and kidney mitochondria to produce ATP was investigated in spontaneously hypertensive rats (SHR). Heart mitochondria from SHR responded to hypertension with tendency to compensate the elevated energy demands of cardiac cells by moderate increase in mitochondrial Mg2+-ATPase activity, membrane fluidity (MF) and in majority of functional parameters of the mitochondria (p>0.05). Significant increase exhibited only the oxygen consumption (QO2; p<0.01-0.001) and oxidative phosphorylation rate (OPR; p<0.003) with glutamate+malate (GLUT+MAL) as substrates. Lowering the blood pressure (p<0.02) captopril also eliminated the above compensatory response and impaired the oxidative ATP production by decreasing OPR (p<0.001). Kidney mitochondria of SHR experienced serious disarrangement in parameters of oxidative ATP production: increase in Mg2+-ATPase activity (p<0.05) but, also scattered QO2 values (p<0.03-0.01) leading to decrease in OPR and the ADP:O (p<0.05-0.01) values with both GLUT+MAL and succinate as substrates. Captopril treatment does not alleviated but even worsened the above alterations. Mg2+-ATPase became also decreased and the depression of ADP:O became aggravated (p<0.0001).

Calcium signaling-mediated endogenous protection of cell energetics in the acutely diabetic myocardium

In acute diabetic myocardium, calcium signals propagated by intracellular calcium transients participate in the protection of cell energetics via upregulating the formation of mitochondrial energy transition pores (ETP). Mechanisms coupling ETP formation with an increase in membrane fluidity and a decrease in transmembrane potential of the mitochondria are discussed. Our results indicate that the amplification of calcium transients in the diabetic heart is associated with an increase in their amplitude. Moreover, the signals transferred by calcium transients also regulated ETP formation in nondiabetic myocardium. Evidence for the indispensable role of calcium in the regulation of transition pore formation is provided whereby an exchange of cadmium for calcium ions led to a rapid and dramatic decrease in the amount of ETP. Another possible regulatory factor of the mitochondrial function may be radical-induced damage to the diabetic heart. Nevertheless, our data indicate that radical-induced changes in mitochondria predominantly concern the respiratory chain and have no appreciable effect on the fluidity of the mitochondrial membranes. The residual mitochondrial production of ATP owing to its augmented transfer to the cytosol proved to be adequate to preserve sufficient levels of adenine nucleotides in the acute diabetic myocardium.

[Characteristics of foot ulcers in diabetic patients]

INTRODUCTION

Diabetic foot syndrome is often presented as a skin lesion in diabetics. The aim of our study was to analyse foot ulcerations in diabetics, together with ethiopatogenesis, location and grade of impairment.

METHODS

We analysed foot ulcerations in 124 diabetics who attended outpatient foot clinic, or were hospitalized in the period from 1996 to 2006. Basic neuropathy screening examination was made with cotton wisp, pin-prick, tuning fork, and monofilament. Beside the evaluation of the presence of pedal pulses, the ankle-brachial pressure index was measured. If the infection of foot ulceration was present, bacteriology examinations was performed. Wagner and University of Texas classifications of foot ulcerations were applied, moreover, location of ulcerations was analysed.

RESULTS

Neuropathic ulcer was diagnosed in 46 patients of the total number of 124 (37%), neuroischemic in 76 patients (61%) and pure ischemic ulcer only in 2 patients (2%). Neuropathy was present in 122 (98%) patients with diabetic foot, limb ischemia in 78 patients (63%). Fifty four per cent of foot ulcers were located on toes and 43% ulcers on plantar surface. Foot ulcer infection was detected in 72 patients (58%). We found 48 superficial ulcers (38.7%) and 76 deep ulcers (61.3%). In diabetics without foot ischemia and infection 39% deep ulcers were present whereas in the group with ischemia and infection the proportion amounted to 80% (p < 0.05).

CONCLUSION

Diabetic foot syndrom was present more often in type-2 diabetics with longer disease duration, in those on insulin treatment, in men of older age, further in the diabetics with pure glycemic control and/or with chronic microvascular diabetic complications.

Polymorphisms of glutathione-S-transferase M1, T1, P1 and the risk of prostate cancer: a case-control study

Background

It has been suggested that polymorphisms in glutathione-S-transferases (GST) could predispose to prostate cancer through a heritable deficiency in detoxification pathways for environmental carcinogens. Yet, studies linking GST polymorphism and prostate cancer have so far failed to unambiguously establish this relation in patients. A retrospective study on healthy, unrelated subjects was conducted in order to estimate the population GST genotype frequencies in the Slovak population of men and compare our results with already published data (GSEC project-Genetic Susceptibility to Environmental Carcinogens). A further aim of the study was to evaluate polymorphisms in GST also in patients with prostate cancer in order to compare the evaluated proportions with those found in the control subjects.

Methods

We determined the GST genotypes in 228 healthy, unrelated subjects who attended regular prostate cancer screening between May 2005 and June 2007 and in 129 histologically verified prostate cancer patients. Analysis for the GST gene polymorphisms was performed by PCR and PCR-RFLP.

Results

We found that the GST frequencies are not significantly different from those estimated in a European multicentre study or from the results published by another group in Slovakia. Our results suggest that Val/Val genotype of GSTP1 gene could modulate the risk of prostate cancer, even if this association did not reach statistical significance. We did not observe significantly different crude rates of the GSTM1 and GSTT1 null genotypes in the men diagnosed with prostate cancer and those in the control group.

Conclusion

Understanding the contribution of GST gene polymorphisms and their interactions with other relevant factors may improve screening diagnostic assays for prostate cancer. We therefore discuss issues of study feasibility, study design, and statistical power, which should be taken into account in planning further trials.

Does rooibos tea (Aspalathus linearis) support regeneration of rat liver after intoxication by carbon tetrachloride?

This study evaluates the effect of rooibos tea (RT, Aspalathus linearis) on biochemical and histological parameters during rat liver regeneration after intoxication by carbon tetrachloride (CCl4). From the 10th week, when the administration of CCl4 was terminated, the liver tissue began to regenerate. Seven days later in the regeneration phase, the animals treated by RT during whole period of the experiment, and those which drunk RT only during the regeneration period, exhibited a trend for decrease in the activity of alanine aminotransferase and significant decrease in the activity of aspartate aminotransferase and in total bilirubin content when compared with the water-drinking group. At the same time, the concentration of plasma albumin was elevated and that of tissue malondialdehyde decreased in the both groups drinking RT. After 42 days of regeneration, all biochemical parameters in all three groups reached the level of control healthy animals. In both groups treated with RT, the extent of fibrotic tissue was lower than in the group which received water. We conclude that RT can be recommended not only for the prevention but also as a co-adjuvant for the therapy of liver diseases.

Endogenous protective mechanisms in remodeling of rat heart mitochondrial membranes in the acute phase of streptozotocin-induced diabetes

The aim of present study was to investigate functional and physical alterations in membranes of heart mitochondria that are associated with remodeling of these organelles in acute phase of streptozotocin-induced diabetes and to elucidate the role of these changes in adaptation of the heart to acute streptozotocin-induced diabetes (evaluated 8 days after single dose streptozotocin application to male Wistar rats). Action of free radicals on the respiratory chain of diabetic-heart mitochondria was manifested by 17 % increase (p<0.05) in oxidized form of the coenzyme Q(10) and resulted in a decrease of states S3 and S4 respiration, the respiratory control index, rate of phosphorylation (all p<0.01) and the mitochondrial transmembrane potential (p<0.05), but the ADP/O ratio decreased only moderately (p>0.05). On the contrary, membrane fluidity and the total mitochondrial Mg2+-ATPase activity increased (both p<0.05). In diabetic heart mitochondria, linear regression analysis revealed a reciprocal relationship between the increase in membrane fluidity and decrease in trans-membrane potential (p<0.05, r = 0.67). Changes in membrane fluidity, transmembrane potential, Mg2+-ATPase activity and the almost preserved ADP/O ratio appear as the manifestation of endogenous protective mechanisms participating in the functional remodeling of mitochondria which contributes to adaptation of the heart to diabetes.

Seasonal variations in properties of healthy and diabetic rat heart mitochondria: Mg2+-ATPase activity, content of conjugated dienes and membrane fluidity

Our previous preliminary results pointed to possible seasonal variations in Mg2+-ATPase activity of rat heart mitochondria (MIT). It is not too surprising since seasonal differences were already reported in myocardial function, metabolism and ultrastructure of the intact as well as hemodynamically overloaded rabbit hearts and also in other tissues. The present study is aimed to elucidate whether seasonal differences observed in rat heart MIT Mg2+-ATPase activity will be accompanied with changes in membrane fluidity and in the content of conjugated dienes (CD) in the lipid bilayers of MIT membranes as well as whether the above seasonal differences will also be present in the diabetic heart. Our results revealed that values of Mg2+-ATPase activity in the winter/spring-period (W/S-P) exceeded significantly (p<0.05-0.001) those in the summer/autumn-period (S/A-P). Similar trend was also observed in hearts of animals with acute (8 days) streptozotocin diabetes. With the exception of values of CD in the S/A-P, all values of Mg2+-ATPase activities, membrane fluidity and CD concentrations in diabetic hearts exceeded those observed in the healthy hearts. Our results indicate that seasonal differences may play a decisive role in the evaluation of properties and function of rat heart MIT.

In vitro evaluation of the cytotoxicity and genotoxicity of resorcylidene aminoguanidine in human diploid cells B-HNF-1

RAG belongs to appropriate inhibitors of protein glycation, i.e. formation of advanced glycation end products, which are thought to be responsible for some complications of DM, including neuropathy, angiopathy, retinopathy and nephropathy. In the present study authors have evaluated the genotoxic effect of RAG on the cell culture of human neonatal fibroblasts (B-HNF-1) in regard to its potential clinical application as inhibitor of advanced glycation end products in relationships to the pathogenesis of chronic diabetic complications. The direct contact cytotoxicity assay and micronucleus test were performed. The results showed that RAG in the concentration range of 1 x 10-4 to 1 x 10-6 mol.l-1 did not induce any changes in the morphology of exposed B-HNF-1 cells. The frequency of micronuclei was not significantly increased as well. The inhibitive effect of resorcylidene aminoguanidine was directly proportional to its concentration. It can be concluded that RAG at the selected concentrations has an inhibitive effect on proliferation of the treated cells and, at the same time, does not display any genotoxic effects on B-HNF-1 cells.

Activity of paraoxonase 1 and lipid profile in healthy children

Paraoxonase 1 (PON1) seems to have a relevant role in detoxifying processes and in atherosclerosis. The aim of this study was to determine PON1 activity, the total antioxidant capacity, as well as entire lipid profile in children for screening of possible risk of atherosclerosis development. Serum PON1 arylesterase/paraoxonase activities were determined spectrophotometrically. The total antioxidant capacity of the serum was measured by TEAC method. Parameters of lipid profile were analyzed by routine laboratory methods. It has been shown that PON1 arylesterase/ paraoxonase activities were very similar to values found in adults. In children, no significant correlation between PON1 arylesterase activity and HDL was observed. PON1 paraoxonase activity correlated only with atherogenic index. PON1 arylesterase activity was significantly higher in girls than in boys. The antioxidant capacity was inversely related to the body mass index. In this study, PON1 activity was determined in healthy children aged 11 to 12 years and we found a similarity in PON1 activities of children and adults. Moreover, the results of our study support the hypothesis that higher body weight of children may contribute to a greater risk for development of atherosclerosis in which oxidative stress plays a role.

Functional remodeling of heart mitochondria in acute diabetes: interrelationships between damage, endogenous protection and adaptation

Rats with streptozotocin-diabetes develop mechanisms of endogenous protection (MEP) that participate actively in functional remodeling of cardiac sarcolemma. Remodeling of sarcolemma is a sign of damage but it also protects the cells of the diabetic heart (DH) against additional energy disbalance due to excessive Ca(2+) entry. Since yet, cardiac mitochondria (MIT) were investigated predominantly from the aspect of damage only. Aims of the present study were: i) to distinguish between acute diabetes-induced changes in function of rat heart MIT which clearly belong to damage from those that reflect the MEP and participate in functional remodeling of the MIT; ii) elucidate the significance of MEP-induced changes in heart MIT for cardiac energetics. Acute diabetes (8 days) was induced in adult male Wistar rats by streptozotocin (STZ, 65 mg.kg(-1) i.p., single dose). On the day 8 after STZ administration, the diabetic animals exhibited 300-330 % increase in blood glucose, triacylglycerols and cholesterol as well as 89.6 % increase in glycohemoglobin (all p < 0.01). The blood level of insulin dropped by 53 % (p < 0.02). State 3 and state 4 oxygen consumptions of DH MIT were decreased against the controls, leading to drop of the respiratory control index (17.9 and 7.3 %) and oxidative phosphorylation rate (OPR, 27.5 and 24.6 %; all p < 0.003-0.02). These effects of damage yielding in strained energy balance of the acute DH were partially alleviated by MEP. The latter involved temporary preservation of the ADP : O ratio, with participation of elevated MIT Mg(2+)-ATPase activity as well as increased formation of MIT substrate and energy transition pores (both p < 0.05). Hence, the energy disbalance of the acute DH was finally manifested in 13 % loss in its AMP content only (p < 0.05). Results indicate that MIT in STZ-DH are functionally remodeled. Defective O2 consumption by MIT renders molecular changes suggestive of a mild hypoxic state but an increase in Mg(2+)-ATPase activity and facilitated energy delivery from MIT to the cytoplasm indicate the presence of MEP acting in the MIT and alleviating the effect of decreased oxidative energy production in the acute DH.

Effect of polyphenolic extract, Pycnogenol, on the level of 8-oxoguanine in children suffering from attention deficit/hyperactivity disorder

The purpose of this randomized, double-blind and placebo controlled study was to test the effect of polyphenolic extract of pine bark Pycnogenol (Pyc) on the level of oxidized purines represented by 8-oxo-7,8-dihydroguanine (8-oxoG) and on the total antioxidant status (TAS) in children with attention deficit/hyperactivity disorder (ADHD).We have found significantly increased damage to DNA in ADHD children when compared to controls. 8-oxoG was significantly lower after 1 month of Pyc administration in comparison to the beginning state and to placebo group. TAS in ADHD children was lower in comparison to controls. After Pyc administration, TAS was elevated but statistically significant increase was recorded after 1 month of termination of Pyc application. Improvement of DNA damage and TAS after Pyc administration is associated with the improvement of attention in ADHD children. In conclusion, Pycnogenol(R) administration reduces oxidative damage to DNA, normalizes TAS and improves attention of ADHD children. Explanation of mutual relation between oxidative damage to DNA, TAS and symptoms of ADHD and mechanism of Pyc's action needs further investigations.

Activity of paraoxonase 1 (PON1) and its relationship to markers of lipoprotein oxidation in healthy Slovaks

Low-density lipoproteins (LDLs), when modified by free radicals derived from artery wall cells, induce atherosclerosis. In contrast to oxidized LDL (ox-LDL), high-density lipoproteins (HDLs) are able to prevent atherosclerosis through a protein with antioxidant properties, paraoxonase 1 (PON1). The purpose of this study was to explore the association between the activity of HDL-associated PON1 and circulating ox-LDL as well as to investigate the relationship between ox-LDL and parameters of lipid profile in thirty Slovaks aged 21-73 years because recent studies have presented controversial results concerning PON1 and its role in LDL oxidation. For determination of circulating ox-LDL sandwich ELISA was used and other lipid parameters were determined by routine laboratory analyses. PON1 activities were assayed by two synthetic substrates - paraoxon and phenyl acetate. Lipid peroxides were determined spectrophotometrically. Of the lipid parameters examined, ox-LDL level correlated positively with total (P < 0.0001) and LDL-cholesterol (P < 0.001). Triacylglycerols (TAG) (P < 0.001), lipid peroxides (P < 0.01) and atherogenic index (AI = total cholesterol/HDL) (P < 0.0001) were also strongly correlated with ox-LDL. No inverse relationships were observed between ox-LDL and HDL-cholesterol or arylesterase/paraoxonase activities of PON1. Furthermore, it was found that ox-LDL (P < 0.01) and lipid peroxides (P < 0.05) were significantly higher in men than in women. PON1 arylesterase activity was marginally affected by sex. The results of this study suggest that the anti-atherogenic properties of HDLs are not directly related to their total concentration and that PON1 activity determined towards synthetic compounds (paraoxon and phenyl acetate) reflects no association with markers of oxidative stress. Furthermore, it follows from our results that men are more susceptible to developing atherosclerosis compared to women.

High glucose contributes to aspirin insensitivity in streptozotocin-diabetic rats: a multiparametric aggregation study

The effect of chronic hyperglycaemia on blood platelet response to acetylsalicylic acid was studied in rats with experimental diabetes. Platelet aggregation was determined in non-diabetic and streptozotocin-diabetic rats treated orally with 4 or 40 mg aspirin (ASA)/kg per day (for 8 weeks from the eighth day of diabetes) using whole blood impedance aggregometry with arachidonic acid or ADP as platelet agonists. The dose-dependent effect of ASA 'therapy' on ADP-agonized platelets was significant only in non-diabetic animals, while in diabetic rats both doses were ineffective in reducing ADP-stimulated platelet aggregation. ASA-mediated increased acetylation of platelet proteins favoured reduced platelet aggregation and slower platelet disaggregation (Pr < 0.025 or less). Interestingly, however, the occupation of platelet protein-free amino groups was significantly higher in control rats compared with diabetic rats (P < 0.001), pointing out that proteins of platelets in non-diabetic animals were more vulnerable for the ASA-induced acetylation. We conclude that chronic hyperglycaemia interferes with preventive effects of ASA on platelet reactivity. Our data validate the suggestion that the relationship between aspirin ineffectiveness and poor metabolic control, first revealed in humans, concerns also other animals' platelets and holds regardless of the model or type of diabetes.

Activity of paraoxonase 1 (PON1) and its relationship to markers of lipoprotein oxidation in healthy Slovaks

Low-density lipoproteins (LDLs), when modified by free radicals derived from artery wall cells, induce atherosclerosis. In contrast to oxidized LDL (ox-LDL), high-density lipoproteins (HDLs) are able to prevent atherosclerosis through a protein with antioxidant properties, paraoxonase 1 (PON1). The purpose of this study was to explore the association between the activity of HDL-associated PON1 and circulating ox-LDL as well as to investigate the relationship between ox-LDL and parameters of lipid profile in thirty Slovaks aged 21-73 years because recent studies have presented controversial results concerning PON1 and its role in LDL oxidation. For determination of circulating ox-LDL sandwich ELISA was used and other lipid parameters were determined by routine laboratory analyses. PON1 activities were assayed by two synthetic substrates - paraoxon and phenyl acetate. Lipid peroxides were determined spectrophotometrically. Of the lipid parameters examined, ox-LDL level correlated positively with total (P < 0.0001) and LDL-cholesterol (P < 0.001). Triacylglycerols (TAG) (P < 0.001), lipid peroxides (P < 0.01) and atherogenic index (AI = total cholesterol/HDL) (P < 0.0001) were also strongly correlated with ox-LDL. No inverse relationships were observed between ox-LDL and HDL-cholesterol or arylesterase/paraoxonase activities of PON1. Furthermore, it was found that ox-LDL (P < 0.01) and lipid peroxides (P < 0.05) were significantly higher in men than in women. PON1 arylesterase activity was marginally affected by sex. The results of this study suggest that the anti-atherogenic properties of HDLs are not directly related to their total concentration and that PON1 activity determined towards synthetic compounds (paraoxon and phenyl acetate) reflects no association with markers of oxidative stress. Furthermore, it follows from our results that men are more susceptible to developing atherosclerosis compared to women.

Increased blood plasma hydrolysis of acetylsalicylic acid in type 2 diabetic patients: a role of plasma esterases

Hydrolysis of acetylsalicylic acid (ASA, aspirin), an antiplatelet drug commonly used in the prevention of stroke and myocardial infarction, seems to play a crucial role in its pharmacological action. Thirty-eight healthy volunteers and 38 type 2 diabetic patients were enrolled to test the hypothesis that the enhanced plasma degradation and lowered bioavailability of ASA in diabetic patients is associated with the attenuation of platelet response. Aspirin esterase activities were tested at pH 7.4 and 5.5. A significantly higher overall aspirin esterase activity was noted at pH 7.4 in the diabetic patients (P<0.003), corresponding to faster ASA hydrolysis (P<0.006). This increased activity was attributable to butyrylcholinesterase and probably to albumin, because it was effectively inhibited by eserine and 4-bis-nitrophenyl phosphate (P<0.01). No significant differences between control and diabetic subjects were found at pH 5.5 in either enzymatic activities or ASA hydrolysis rates. The enhanced plasma ASA degradation in diabetic subjects was significantly associated with the refractoriness of blood platelets to ASA (P<0.05) and modulated by plasma cholesterol (P<0.01). No direct effects of plasma pH or albumin were observed. In conclusion, higher aspirin esterase activity contributes to the lowered response of diabetic platelets to ASA-mediated antiplatelet therapy.

The effect of Pycnogenol on the erythrocyte membrane fluidity

In the present study, the in vitro effect of polyphenol rich plant extract, flavonoid--Pycnogenol (Pyc), on erythrocyte membrane fluidity was studied. Membrane fluidity was determined using 1-[4-trimethyl-aminophenyl]-6-phenyl-1,3,5-hexatriene (TMA-DPH), 1,6-diphenyl-1,3,5-hexatriene (DPH) and 12-(9-anthroyloxy) stearic acid (12-AS) fluorescence anisotropy. After Pyc action (50 microg/ml to 300 microg/ml), we observed decreases in the anisotropy values of TMA-DPH and DPH in a dose-dependent manner compared with the untreated erythrocyte membranes. Pyc significantly increased the membrane fluidity predominantly at the membrane surface. Further, we observed the protective effect of Pyc against lipid peroxidation, TBARP generation and oxidative hemolysis induced by H2O2. Pyc can reduce the lipid peroxidation and oxidative hemolysis either by quenching free radicals or by chelating metal ions, or by both. The exact mechanism(s) of the positive effect of Pyc is not known. We assume that Pyc efficacy to modify effectively some membrane dependent processes is related not only to the chemical action of Pyc but also to its ability to interact directly with cell membranes and/or penetrate the membrane thus inducing modification of the lipid bilayer and lipid-protein interactions.

Remodelling of the sarcolemma in diabetic rat hearts: the role of membrane fluidity

The hyperglycaemia and oxidative stress, that occur in diabetes mellitus, cause impairment of membrane functions in cardiomyocytes. Also reduced sensitivity to Ca-overload was reported in diabetic hearts (D). This enhanced calcium resistance is based on remodelling of the sarcolemmal membranes (SL) with down-regulated, but from the point of view of kinetics relatively well preserved Na,K-ATPase and abnormal Mg- and Ca-ATPase (Mg/Ca-ATPase) activities. It was hypothesised that in these changes may also participate the non-enzymatic glycation of proteins (NEG) and the related free radical formation (FRF), that decrease the membrane fluidity (SLMF), which is in reversal relationship to the fluorescence anisotropy (D 0.235 +/- 0.022; controls (C) 0.185 +/- 0.009; p < 0.001). In order to check the true role of SLMF in hearts of the diabetic rats (streptozotocin, single dose, 45 mg/kg i.v.) animals were treated in a special regimen with resorcylidene aminoguanidine (RAG 4 mg/kg i.m.). The treatment with RAG eliminated completely the diabetes-induced decrease in the SLMF (C 0.185 +/- 0.009; D + RAG 0.167 +/- 0.013; p < 0.001) as well as in NEG (fructosamine microg x mg(-1) of protein: C 2.68 +/- 0.14; D 4.48 +/- 0.85; D + RAG 2.57 +/- 0.14; p < 0.001), and FRF in the SL (malondialdehyde: C 5.3 +/- 0.3; D 8.63 +/- 0.2; D + RAG 5.61 +/- 0.53 micromol x g(-1); p < 0.05). Nevertheless, the SL ATPase activity in diabetic animals was not considerably influenced by RAG (increase in D + RAG vs. D 3.3%, p > 0.05). On the other hand, RAG increased considerably the vulnerability of the diabetic heart to overload with external Ca2+ (C 100% of hearts failed, D 83.3%, D + RAG 46.7% of hearts survived). So we may conclude, that: (i) The NEG and FRF caused alterations in SLMF, that accompanied the diabetes-induced remodelling of SL, also seem to participate in the protection of diabetic heart against Ca2+-overload; (ii) Although, the changes in SLMF were shown to influence considerably the ATPase activities in cells of diverse tissues, they seem to be little responsible for changes in ATPases-mediated processes in the SL of chronic diabetic hearts.