d-glucaro 1,4-lactone and resveratrol as antioxidants in blood platelets

The aim of our work was to study the anti-aggregatory and antioxidative effects of natural dietary products, d-glucaro 1,4-lactone (1,4-GL) in combination with phenolic compound resveratrol (trans-3,4′,5-trihydroxystilbene). Our results in vitro showed that 1,4-GL alone slightly inhibits platelet aggregation induced by thrombin. The combination of resveratrol (0.1 μM) with 0.5 mM of 1,4-GL caused a significant decrease of thrombin-induced platelet aggregation; however separately, neither of studied compound at used concentrations was not effective. When platelets were treated with 1,4-GL (at the concentration of 0.1 mM and higher) and resveratrol (0.1 μM), similar synergistic action of both tested compound on markers of oxidative stress formation was observed. We measured the levels of different specific markers of oxidative stress, e.g., superoxide anion radicals , thiobarbituric acid-reactive substances and carbonyl group formation. Both tested compounds inhibited also the generation of and malondialdehyde that represents enzymatical peroxidation of arachidonic acid leading to thromboxane A₂ (TXA₂) formation in platelets after thrombin stimulation. The obtained in vitro results demonstrate that anti-platelet and antioxidative properties of resveratrol may be significantly augmented by another dietary agent such as 1,4-GL, but mechanism synergistic action of these compounds is not yet known.     

CC2D2A, encoding a coiled-coil and C2 domain protein, causes autosomal-recessive mental retardation with retinitis pigmentosa

Autosomal-recessive inheritance is believed to be relatively common in mental retardation (MR), although only four genes for nonsyndromic autosomal-recessive mental retardation (ARMR) have been reported. In this study, we ascertained a consanguineous Pakistani family with ARMR in four living individuals from three branches of the family, plus an additional affected individual later identified as a phenocopy. Retinitis pigmentosa was present in affected individuals, but no other features suggestive of a syndromic form of MR were found. We used Affymetrix 500K microarrays to perform homozygosity mapping and identified a homozygous and haploidentical region of 11.2 Mb on chromosome 4p15.33-p15.2. Linkage analysis across this region produced a maximum two-point LOD score of 3.59. We sequenced genes within the critical region and identified a homozygous splice-site mutation segregating in the family, within a coiled-coil and C2 domain-containing gene, CC2D2A. This mutation leads to the skipping of exon 19, resulting in a frameshift and a truncated protein lacking the C2 domain. Conservation analysis for CC2D2A suggests a functional domain near the C terminus as well as the C2 domain. Preliminary functional studies of CC2D2A suggest a possible role in Ca(2+)-dependent signal transduction. Identifying the function of CC2D2A, and a possible common pathway with CC2D1A, in correct neuronal development and functioning may help identify possible therapeutic targets for MR.     

Kinetic properties of Cellulomonas sp. purine nucleoside phosphorylase with typical and non-typical substrates: implications for the reaction mechanism

Phosphorolysis catalyzed by Cellulomonas sp. PNP with typical nucleoside substrate, inosine (Ino), and non-typical 7-methylguanosine (m7Guo), with either nucleoside or phosphate (Pd) as the varied substrate, kinetics of the reverse synthetic reaction with guanine (Gua) and ribose-1-phosphate (R1P) as the varied substrates, and product inhibition patterns of synthetic and phosphorolytic reaction pathways were studied by steady-state kinetic methods. It is concluded that, like for mammalian trimeric PNP, complex kinetic characteristics observed for Cellulomonas enzyme results from simultaneous occurrence of three phenomena. These are sequential but random, not ordered binding of substrates, tight binding of one substrate purine bases, leading to the circumstances that for such substrates (products) rapid-equilibrium assumptions do not hold, and a dual role of Pi, a substrate, and also a reaction modifier that helps to release a tightly bound purine base.     

Differences in the activities of some antioxidant enzymes and in H2O2 content during rhizogenesis and somatic embryogenesis in callus cultures of the ice plant

Callus was obtained from hypocotyls of Mesembryanthemum crystallinum seedlings cultured on two types of medium—germination medium (GM) and callus induction medium (CIM). Following subculture on shoot induction medium SIM1, the callus formed on CIM medium regenerated roots or somatic embryos, while that obtained on GM medium was non-regenerative. The activities of CuZn-superoxidase dismutase (SOD) were comparable in all calli, but the activities of FeSOD and MnSOD varied according to the activity of photosystem II and the regenerative potential of the tissues. Catalase (CAT) activity was related to H₂O₂ concentration and affected by both the culture conditions and the morphogenic potential of the calli. The possible role of CAT, SODs and H₂O₂ in the regeneration of M. crystallinum from callus is discussed.This work is dedicated to Prof. Dr. Hubert Ziegler on his 80th birthday.     

Methods of assessment and clinical relevance of QT dynamics

The dependence on heart rate of the QT interval has been investigated for many years and several mathematical formulae have been proposed to describe the QT interval/heart rate (or QT interval/RR interval) relationship. While the most popular is Bazett's formula, it overcorrects the QT interval at high heart rates and under-corrects it at slow heart rates. This formulae and many others similar ones, do not accurately describe the natural behaviour of the QT interval. The QT interval/RR interval relationship is generally described as QT dynamics. In recent years, several methods of its assessment have been proposed, the most popular of which is linear regression. An increased steepness of the linear QT/RR slope correlates with the risk of arrhythmic death following myocardial infarction. It has also been demonstrated that the QT interval adapts to heart rate changes with a delay (QT hysteresis) and that QT dynamics parameters vary over time. New methods of QT dynamics assessment that take into account these phenomena have been proposed. Using these methods, changes in QT dynamics have been observed in patients with advanced heart failure, and during morning hours in patients with ischemic heart disease and history of cardiac arrest. The assessment of QT dynamics is a new and promising tool for identifying patients at increased risk of arrhythmic events and for studying the effect of drugs on ventricular repolarisation.     

The influence of structure and redox state of prenylquinones on thermotropic phase behaviour of phospholipids in model membranes

Our study was aimed to investigate the significance of the isoprenoid side chain size as well as redox state of the quinone ring for interaction of two main classes of prenylquinones: plastoquinones (PQ) and ubiquinones (UQ) with lipid bilayers. By use of differential scanning calorimetry (DSC) we have followed the thermotropic behaviour of multilamellar vesicles prepared from dipalmitoylphosphatidylcholine (DPPC) upon incorporation of increasing amount (1.3-12 mol%) of quinone (quinol) molecules. Our studies reveal that as the side chain is shorter (from 9 to 2 isoprenoid units) the height of the calorimetric profiles is reduced and the temperature of the main transition of DPPC (T(m)) decreases (T(m)=39.4 degrees C for a sample with 12 mol% of PQ-2), and then increases up to 39.8 degrees C for PQ-1. For the samples containing quinols the effect is more pronounced even at lower concentration. The greater influence of the added prenylquinones on the pretransition demonstrates a stronger distortion of the DPPC packing in the gel state. It seems that this is the isoprenoid side chain length rather than the redox state of prenylquinones that determines their effectiveness in perturbation of thermotropic properties of lipid bilayer.     

Selenium status in psoriasis and its relationship with alcohol consumption

The aim of the study was to examine the influence of alcohol consumption on the severity of psoriasis and selenium (Se) concentration and Se-dependent gluathione peroxidase activity in plasma (pl-GSH-Px) and in erythrocytes (RBC-GSH-Px) in psoriatic patients. Thirty-five in-patients with psoriasis lasting <10 mo and 42 with psoriasis lasting >3 yr constituted groups 1 and 2, respectively. The severity of psoriasis was assessed using the PASI scoring system and the consumption of alcohol, using a structured questionnaire. The Se concentration was 47.11±11.61 μg/L in group 1 and 38.69±13.22 μg/L in group 2 (p<0.05), the pl-GSH-Px was 0.15±0.04 U/mL and 0.14±0.04 U/mL (p>0.05), and the RBC-GSH-Px was 13.97±4.27 U/g Hb and 13.16±3.85 U/g Hb (p>0.05), respectively. In excessive drinkers (<10% of patients, all males), the Se concentration was 32.84±10.88 μg/L, the pl-GSH-Px was 0.15±0.03 U/mL, and the RBC-GSH-Px was 11.64±3.32 U/g Hb. A low RBC-GSH-Px correlated to the consumption of high-grade alcoholic beverages (R=−0.45, p<0.05) and to the PASI value (R=−0.37, p<0.05) in group 2. Depressed Se concentration and Se-dependent GSH-Px can be related to the severity and a duration of psoriasis. The excessive consumption of alcohol is associated with severity of the disease and with low activity of GSH-Px in erythrocytes in patients with long-lasting psoriasis.