Positive inotropic effects of epigallocatechin-3-gallate (EGCG) involve activation of Na+/H+ and Na+/Ca2+ exchangers

BACKGROUND

There is evidence that the tea catechin epigallocatechin-3-gallate (EGCG) modulates myocardial contractility. However, the underlying mechanisms remain to be determined.

AIMS

To study potential signalling pathways involved in EGCG-induced contractile parameters.

METHODS AND RESULTS

EGCG increased fractional shortening in rat cardiac myocytes and enhanced intracellular systolic Ca2+ concentrations. In isolated rat hearts, perfusion with EGCG resulted in significant, dose-dependent increase in peak systolic left ventricular pressure, as well as in contraction and relaxation velocities. Heart rate did not change. Inhibition of the beta1-receptor with metoprolol had no influence on the contractile effects of EGCG. Furthermore, levels of cAMP and phosphorylation of phospholamban did not change with EGCG, indicating that the beta-receptor pathway is not involved. The L-type Ca2+ channel inhibitors, nifedipine and gallopamil, failed to modulate EGCG-induced increase in contractility. However, the myocardial effects and intracellular calcium transients stimulated by EGCG were significantly reduced by the antagonist of the Na+/H+ exchanger (NHE) methyl-N-isobutyl amiloride (MIA), and by blocking of the reverse mode of the Na+/Ca2+ exchanger (NCX) by KB-R7943.

CONCLUSION

These results indicate that Ca2+-dependent positive inotropic and lusitropic effects of EGCG are mediated in part via activation of the Na+/H+ exchanger and the reverse mode of the Na+/Ca2+ exchanger in the rat myocardium.

Spatial fluctuations of optical emission from single ZnO/MgZnO nanowire quantum wells

MgZnO/ZnO quantum wells on top of ZnO nanowires were grown by pulsed laser deposition. Ensembles of spatially fluctuating and narrow cathodoluminescence peaks with single widths down to 1 meV were found at the spectral position of the quantum well emission at 4 K. In addition, the number of these narrow QW peaks increases with increasing excitation power in micro-photoluminescence, thus pointing to quantum-dot-like emission centers. Indeed, laterally strained areas of about 5 nm diameter were identified at the quantum well positions on top of the nanowires by high-resolution transmission electron microscopy.

Deployment of the encapsulation-dehydration protocol to cryopreserve microalgae held at the Sammlung von Algenkulturen, Universitat Gottingen, Germany

Encapsulation-dehydration was applied to cryopreserve 14 diverse algal strains, representing eukaryotic terrestrial microalgae; of these 12 survived to form cell colonies after recovery from cryostorage. Surviving algae had varying degrees of tolerance to osmotic dehydration and desiccation in this vitrification-based cryoprotective strategy. The extent of algal regrowth was affected by the mode of desiccation (silica gel or air-flow), the duration of evaporative desiccation and exposure to light during early recovery phase. This paper: (i) demonstrates the versatility of the encapsulation/dehydration method to cryopreserve diverse microalgae; (ii) confirms the successful transfer of this cryostorage technology to the Culture Collection of Algae at Gottingen University (SAG); and (iii) recommends encapsulation/dehydration as a feasible alternative to controlled rate cooling for preserving algae held in international culture collections.

Ultrasensitive Determination of Polycyclic Aromatic Compounds with Atmospheric-Pressure Laser Ionization as an Interface for GC/MS

Recently we introduced atmospheric pressure laser ionization (APLI) as a complementary ionization method for coupling LC-MS systems (HPLC and CEC), allowing ionization of nonpolar aromatic compounds via near-resonant two-photon excitation. In this paper, we demonstrate that APLI with the same source enclosure as for LC coupling is also suited for hyphenation of GC with atmospheric-pressure ionization mass spectrometry. This technique permits the qualitative and quantitative determination of aromatic compounds in an ultralow concentration range, as we show here with polycyclic aromatic hydrocarbons (PAHs), alkylated PAHs, and hetero-PAHs as examples. The outstanding sensitivity is demonstrated for chrysene, with a detection limit of 22 amol. Polar functional groups reduce the sensitivity, but after methylation or silylation, the analytes can also be determined very sensitively in complex matrixes, as is shown with 1-hydroxypyrene in urine.

Alternative splicing in intron 13 of the human eNOS gene: a potential mechanism for regulating eNOS activity

NO, the product of endothelial NOS (eNOS), is a major regulator of vascular homeostasis and a critical factor in preventing cardiovascular diseases. We previously established a positive correlation between the number of variable CA repeats in intron 13 of human eNOS and the risk of coronary artery disease, and demonstrated that these polymorphic CA repeats function as a length-dependent splicing enhancer. By 5'-RACE polymerase chain reaction (PCR), we detected three splice variants containing novel 3' splice sites within intron 13--termed eNOS13A, eNOS13B, and eNOS13C--which share the first 13 exons of human eNOS and the same polyadenylation site at the end of the novel exon. When translated, all these splice variants would result in truncated proteins lacking eNOS activity. Coexpression of full-length eNOS with eNOS13A diminished eNOS enzyme activity in COS-7 cells by formation of heterodimers. The splice variants were expressed in endothelial cells and various human tissues. Finally, we demonstrate, using minigene transfection, that the expression of the eNOS13A splice variant is increased with high CA repeat numbers in intron 13. These data suggest a new mechanism for the regulation of eNOS activity and NO production in the cardiovascular system by truncated, dominant-negative splice variants of human eNOS.

Molecular targets of tea polyphenols in the cardiovascular system

Tea-derived polyphenols have attracted considerable attention in the prevention of cancer and cardiovascular diseases. In comparison to tumour cells, the elucidation of their molecular targets in cardiovascular relevant cells is still at the beginning. Although promising experimental and clinical data demonstrate protective effects for the cardiovascular system, little information is actually available on how these beneficial effects of tea polyphenols are mediated at the cellular level. By affecting the activity of receptor and signal transduction kinases, both catechins and theaflavins--the major ingredients of green and black tea, respectively--exert a variety of cardiovascular beneficial effects. In general, the number and positions of galloyl groups have major influence on the potency of polyphenols. Compared to their broad impact on cellular signal transduction, tea polyphenols reveal little transcriptional effects. However, more detailed and profound analysis of molecular actions in different cells of the cardiovascular system is necessary before safe clinical use of tea polyphenols for treatment of cardiovascular diseases will become possible.

Comparison of reactive oxygen species concentration in seminal plasma and semen parameters in partners of pregnant and non-pregnant patients after IVF/ICSI

The aims of this study were (i) to determine and compare the concentration of reactive oxygen species (ROS) and total antioxidant status (TAS) in seminal plasma and sperm parameters of the male partners of patients undergoing IVF or intracytoplasmic sperm injection (ICSI) treatment and (ii) to establish the relationship between ROS and TAS concentrations and sperm quality and their effect on fertilization and pregnancy rate of patients who achieved a pregnancy and those who were unsuccessful. Twenty-six IVF and 22 ICSI patients were included in this study. The ROS concentration in seminal plasma and sperm concentration, vitality (eosin test), motility, morphology, membrane integrity (HOS test), maturity (chromomycin, CMA3) and DNA fragmentation (TUNEL) results and their relationship to fertilization and pregnancy were analysed. ROS concentrations were similar regarding the seminal plasma of male partners of patients who achieved a pregnancy and those who were unsuccessful. The other semen parameters, concentration, motility, vitality, membrane and DNA integrity, were comparable in both groups. However, both groups demonstrated a negative correlation between ROS concentration and sperm vitality, membrane integrity and morphology. Moreover, an inverse correlation was found between TUNEL, vitality, and membrane integrity. In conclusion, ROS concentration in seminal plasma affects the quality of spermatozoa. A negative correlation between the ROS concentration in seminal plasma and fertilization rate in both IVF/ICSI programmes was shown.

Real-time interaction with a humanoid avatar in an immersive table tennis simulation

In this paper, we report on the realization of an immersive table tennis simulation. After describing the hardware necessities of our system, we give insight into different aspects of the simulation. In particular, the developed methods for collision detection and physical simulation are presented. The design of the virtual opponent is of crucial importance to realize an enjoyable game. Therefore, we report on the implemented game strategy and the animation of the opponent. Since table tennis is one of the fastest sports, the synchronization of the human player's movements and the visual output on the projection wall is a very challenging problem to solve. To overcome the latencies in our system, we designed a prediction method that allows high speed interaction with our application.

[Evaluation of different protocols for the leg cuff technique for measurement of dynamic cerebral autoregulation]

AIM

Aaslid's leg cuff method is a well validated technique to measure dynamic cerebral autoregulation. In the literature different protocols to choose cuff pressure have been described. The aim of this study is to find a technique as accurate as possible without un-necessary inconvenience for the patient.

METHOD

The leg cuff test with bilateral cuffs was performed on 10 young healthy volunteers with three different protocols (cuff pressure at systolic level, doppler controlled and 30 mmHg above systolic level). For each examination the autoregulation index invented by Tiecks and Mahony was calculated. Statistical modelling of correlated data was done with Generalized Estimating Equations.

RESULTS

The choice of the protocol influences the quality of the actual autoregulation test. The most reliable protocol is also the most inconvenient one for the patient. We found no systematic bias of the protocol on the autoregulation index, but the relation between induced blood pressure drop and resulting autoregulation index was close to statistical significance.

CONCLUSION

For the leg cuff test with bilateral cuffs in awake patients we recommend to apply the protocol proposed by Tiecks. Additional report of the magnitude of induced blood pressure drop would be helpful to improve the results' comparability.

Nontoxic proteasome inhibition activates a protective antioxidant defense response in endothelial cells

Inhibitors of the ubiquitin-proteasome system offer a new and promising approach in the therapy of proliferative and inflammatory diseases. In order to narrow the therapeutic window for cytotoxic effects on the one hand and nontoxic, anti-inflammatory effects on the other hand, we elucidated the complex cellular effects of toxic versus nontoxic proteasome inhibition in human endothelial cells by expressional profiling. Nontoxic doses of proteasome inhibitors induced a defined, dose-dependent transcriptional response that was markedly attenuated in terms of gene number and amplitude of regulation compared to toxic doses. In particular, we observed uniform upregulation of several antioxidative enzymes and differential regulation of genes involved in endothelial function. This adaptive transcriptional pattern was translated into a protective response of endothelial cells against H(2)O(2)-induced oxidative stress and into improvement of endothelial function of rat aortic rings. Our data thus suggest that nontoxic proteasome inhibition might offer a new therapeutic approach for the treatment of endothelial dysfunction in cardiovascular disorders.

Addition of milk prevents vascular protective effects of tea

AIMS

Experimental and clinical studies indicate that tea exerts protection against cardiovascular diseases. However, a question of much debate is whether addition of milk modifies the biological activities of tea. We studied the vascular effects of tea, with or without milk, in humans and elucidated the impact of individual milk proteins in cell culture experiments, with isolated rat aortic rings and by HPLC analysis.

METHODS AND RESULTS

A total of 16 healthy female volunteers consumed either 500 mL of freshly brewed black tea, black tea with 10% skimmed milk, or boiled water as control. Flow-mediated dilation (FMD) was measured by high-resolution vascular ultrasound before and 2 h after consumption. Black tea significantly improved FMD in humans compared with water, whereas addition of milk completely blunted the effects of tea. To support these findings, similar experiments were performed in isolated rat aortic rings and endothelial cells. Tea induced vasorelaxation in rat aortic rings and increased the activity of endothelial nitric oxide synthase by phosphorylation of the enzyme in endothelial cells. All effects were completely inhibited by the addition of milk to tea. Of the various kinds of milk proteins, the caseins accounted for these inhibiting effects of milk, probably by formation of complexes with tea catechins.

CONCLUSION

Milk counteracts the favourable health effects of tea on vascular function. This finding indicates the need for particular awareness in the interpretation and design of studies comprising nutritional flavonoids.

The role of tea and tea flavonoids in cardiovascular health

Consumption of green or black tea has been inversely associated with the development and progression of cardiovascular diseases. In this review, the current knowledge about protective effects of tea and tea constituents, particularly flavonoids, on the cardiovascular system is summarized. Underlying mechanisms for the beneficial effects of tea include vasculoprotective, antioxidative, antithrombogenic, anti-inflammatory, and lipid-lowering properties of tea flavonoids. Although promising experimental data on beneficial effects of tea in various cardiovascular diseases are available, results of clinical studies in humans are not uniform. A number of factors are discussed which may contribute to inconsistent data in humans. Overall, tea represents a promising tool for the prevention and treatment of cardiovascular disorders.

Hemi-spinal cord infarction due to vertebral artery dissection in congenital afibrinogenemia

Isolated ischemia of the cervical spinal cord is an uncommon but increasingly recognized complication of vertebral artery dissection (VAD). The authors report a young patient with congenital afibrinogenemia, who developed VAD with extensive unilateral spinal cord infarction, probably caused by local compression of spinal radicular feeders at their origin by vertebral artery hematoma.

Anaemia after renal transplantation

Anaemia is a frequent complication among long-term renal transplant recipients. A prevalence of approximately 40% has been reported in several studies. If renal function declines to stage 5 kidney disease, the prevalence of anaemia in kidney transplants is even higher. A positive correlation between haemoglobin concentration and creatinine clearance has been reported, which is a function of endogenous erythropoietin production by the functioning graft. Inflammation related to a retained kidney graft may cause hypo-responsiveness to erythropoietic agents once kidney transplant recipients return to dialysis. Furthermore, the use of azathioprine, mycophenolate mofetil and sirolimus may be associated with post-transplant anaemia. Along with erythropoietin deficiency, depletion of iron stores is one of the major reasons for anaemia in the kidney transplant population. The proportion of hypochromic red blood cells appears to be a useful parameter to measure iron supply and utilization as well as to estimate mortality risks in kidney transplant recipients. While anaemia is an important cardiovascular risk-factor after transplantation, our data suggest that anaemia is not associated with mortality and graft loss. Nevertheless, inadequate attention is paid so far to the management of anaemia after renal transplantation. A promising future aspect for risk reduction of cardiovascular disease includes the effect of erythropoietic agents on endothelial progenitor cells.