Biomedical subjects

W Bloch

Publications and source records attributed to W Bloch.

At least 19 recordsLinked to original sources

PubMed2006

Exercise has a positive effect on endothelial progenitor cells, which could be necessary for vascular adaptation processes.

Since many years, it was believed that the sole mechanism for postnatal growth of new blood vessels in response to exercise is angiogenesis, occurring through vascular sprouting and intucesseption. Today, accumulating evidence indicates that peripheral blood contains marrow-derived endothelial progenitor cells, which have the potential to differentiate into mature endothelial cells and which can contribute to postnatal vessel growth and repair (postnatal vasculogenesis). However, controversy exists with respect to the identification and the origin of endothelial progenitor cells, this review focus on the different possible sources of endothelial progenitor cells like hematopoietic stem cells, monocytes/macrophages, and mesenchymal stem cells (multipotent adult progenitor cells; MAPCs). In the last years, several groups were able to show the positive effects of exercise on endothelial progenitor cells, which means that vasculogenesis/endothelial progenitor cells might as well contribute to the growth of new blood vessels in adaptation processes. The effect of exercise on endothelial progenitor cells and possible mobilization-factors like hypoxia are discussed.

Adaptation, Physiological↗

PubMed2006

Increased Ca2+ sensitivity and protein expression of SERCA 2a in situations of chronic beta3-adrenoceptor deficiency.

This study investigated the influence of chronic beta(3)-adrenoceptor deficiency on myocardial function. Therefore, we investigated Ca(2+)-regulatory proteins, SERCA 2a activity, and myofibrillar and mitochondrial function in hearts of wild-type (WT, n=7) and beta(3)-adrenoceptor knockout mice (beta(3)-KNO, n=7). Morphometric heart analysis showed no difference between WT and beta(3)-KNO. No alterations were observed for the protein expression of the ryanodine receptor or phospholamban. However, in beta(3)-KNO mice, protein expression of SERCA 2a and phospholamban phosphorylation were significantly increased. These changes were accompanied by an increased SERCA 2a activity in beta(3)-KNO. Alterations in phospholamban phosphorylation were independent of alterations in beta(1)/beta(2)-adrenoceptor distribution and protein expression of G proteins in beta(3)-KNO. Measurement of myofibrillar Ca(2+) sensitivity showed no difference in the Ca(2+)/force relation for WT and beta(3)-KNO. The same seems to hold true for mitochondrial function since the protein expressions of cytochrome c, uncoupling protein 3 and cytochrome c oxidase subunit IV were similar in WT and beta(3)-KNO. The conclusion is that depression of beta(3)-adrenergic stimulation may modulate the protein expression of SERCA 2a and phospholamban phosphorylation, thereby improving sarcoplasmic reticulum Ca(2+) uptake. Thus, beta(3)-adrenergic depression may be a therapeutic aim in situations of impaired SERCA 2a activity, e.g. for the treatment of heart failure.

Animals↗

PubMed2006

Endostatin, the proteolytic fragment of collagen XVIII, induces vasorelaxation.

Collagen XVIII is an important component of the extracellular matrix and is expressed in basement membranes. Its degradation results in the generation of endostatin claimed to possess antiangiogenic activity. To date, only limited knowledge exists with regard to the cellular signaling of this molecule. We show in single-cell measurements using the Ca2+ indicator fura-2 acetoxy methylester (fura-2 AM) and the nitric oxide (NO) indicator 4,5-diaminofluorescein diacetate that application of endostatin (ES) (5 pmol/L, 100 ng/mL) induced Ca2+ spikes and an increase of NO production in human and murine endothelial cells. The NO response was independent of an increase in cytosolic Ca2+ and blocked by the endothelial NO synthase (eNOS) inhibitor NG-nitro-L-arginine methyl ester and by incubation with pertussis toxin known to inhibit G(i/o) proteins. The physiological relevance of this novel signaling pathway of ES was assessed with isometric force measurements in large and small arteries of mouse. Physiological concentrations of ES were found to decrease vascular tone in an endothelium-dependent manner. This occurred via an Arg-Gly-Asp (RGD) peptide-independent pathway through activation of G(i/o) proteins, phosphatidylinositol 3-kinase, Akt, and eNOS. We conclude that the proteolytic matrix fragment ES is a prominent vasorelaxing agent. Because ES is constantly released into the blood, it is a novel regulator of blood pressure and, therefore, represents an interesting pharmacological target.

Animals↗

PubMed2006

8-Isoprostane is a dose-related biomarker for photo-oxidative ultraviolet (UV) B damage in vivo: a pilot study with personal UV dosimetry.

BACKGROUND: Ultraviolet (UV) B irradiation causes visible erythema, which has been linked with DNA damage. However, besides such direct photochemical conformation changes, UVB also induces many indirect photochemical effects in the skin. Lipid peroxidation (LPO) is in this context one of the major pathways by which photo-oxidative stress disturbs cell signalling and promotes photocarcinogenesis and photoageing. So far we lack techniques for visualizing photo-oxidative stress in the skin. Furthermore, LPO has never been linked with individually acquired UVB doses measured by personal dosimetry. OBJECTIVES: Measuring the skin reaction and photo-oxidative damage by LPO in vivo after UVB exposure in a pilot study surveyed by personal dosimetry in order to allow for a correlation analysis of acquired dose, skin reaction and amount of LPO. METHODS: UVB exposure was measured with the opto-electronic X2000-1 (Gigahertz Optik, Puchheim, Germany) and the biological DLR Biofilm (German Aerospace Center DLR, Cologne, Germany) portable dosimeter. The skin reaction following UVB exposure was quantified with a Minolta chromameter (Minolta, Tokyo, Japan) and LPO in vivo was measured by 8-isoprostane generation by means of densitometric analysis of immunohistochemical samples obtained 30 min post-UVB irradiation. RESULTS: Regression analysis revealed significant linear relations between UVB exposures recorded by the dosimeters and colorimetry parameters of the skin reaction. Furthermore, an even better linear relation with higher significance was found between the generation of 8-isoprostane in the skin and the dosimeter readouts. CONCLUSIONS: LPO measured by the generation of 8-isoprostane provides a suitable intrinsic biomarker for photo-oxidative UVB damage in vivo. This study provides a new approach to visualizing photo-oxidative stress in the skin in vivo. Furthermore, future dosimeter readouts can now be set into relation to the expected increase of LPO that can be calculated within the limits of our study.

Adult↗

PubMed2006

Bradykinin mediates phosphorylation of eNOS in odontoblasts.

While the activation of eNOS by Akt/PKB-dependent phosphorylation, leading to NO release, and the inhibition of enzyme activity by bradykinin (BK)-mediated phosphorylation of eNOS in endothelial cells are established, the phosphorylation of eNOS in odontoblasts is unknown. To clarify the regulation of eNOS in odontoblasts by BK, we examined the phosphorylation of eNOS, Akt/PKB, and ERK1/2 in odontoblasts of rat molars. BK (10(-7) M) transiently induced the phosphorylation of eNOS at Ser1177, Akt/PKB in odontoblasts, while it induced the phosphorylation of eNOS at Thr495 throughout the entire period of BK treatment. BK receptor 2 antagonist HOE 140 (10(-6) M) significantly reduced signal intensities of phosphorylated-eNOS at Ser1177, Thr495, and phosphorylated-Akt/PKB. These results suggest that BK has dual effects on the activation of eNOS in odontoblasts, the Akt/PKB-dependent up-regulation of eNOS by the transient phosphorylation at Ser1177, and the ERK1/2-independent down-regulation of eNOS by the phosphorylation at Thr495.

Animals↗

PubMed2006

Beta3-adrenergic stimulation in the human heart: signal transduction, functional implications and therapeutic perspectives.

Next to beta1- and beta2-adrenoceptors, a third beta-adrenoceptor population is expressed in the human heart, the beta3-adrenoceptor. In mammalian ventricular myocytes, beta3-adrenergic stimulation leads to a decrease in contractility via a release of nitric oxide (NO). Recently, different molecular mechanisms of beta3-adrenergic activation of endothelial nitric oxide synthase (eNOS) have been uncovered in cardiac myocytes. In the non-failing and especially the failing heart, beta3-adrenergic stimulation may offer protection against excessive catecholaminergic beta1-adrenoceptor stimulation. In this context, the beta3-adrenoceptor is discussed as a novel target for the pharmacological therapy of heart failure.

Adrenergic beta-3 Receptor Agonists↗

PubMed2005

Identification and characterization of embryonic stem cell-derived pacemaker and atrial cardiomyocytes.

The aim of this study was to identify and functionally characterize cardiac subtypes during early stages of development. For this purpose, transgenic embryonic stem cells were generated using the alpha-myosin heavy chain promoter driving the expression of the enhanced green fluorescent protein (EGFP). EGFP-positive clusters of cells were first observed as early as 7 days of development, thus, even before the initiation of the contractile activity. Flow cytometry and single-cell fluorescence measurements evidenced large diversities of EGFP intensity. Patch-clamp experiments showed EGFP expression exclusively in pacemaker and atrial but not ventricular cells. The highest fluorescence intensities were detected in pacemaker-like cardiomyocytes. In accordance, multielectrode-array recordings of whole embryoid bodies confirmed that the pacemaker center coincided with strongly EGFP-positive areas. The cardiac subtypes displayed already at this early stage differential characteristics of electrical activity and ion channel expression. Thus, quantitation of the alpha-myosin heavy chain driven reporter gene expression allows identification and functional characterization of early cardiac subtypes.

Animals↗

PubMed2005

NO-cGMP signaling molecules in cells of the rat molar dentin-pulp complex.

By the formation of cyclic guanosine 3',5'-monophosphate (cGMP), nitric oxide (NO)-sensitive enzyme-soluble guanylate cyclase (sGC) plays a receptor role for NO within the NO-cGMP signaling cascade, which is involved in vasodilatation and neurotransmission. The hypothesis that NO-cGMP signaling molecules modulate cells of the dentin-pulp complex was investigated in rat molars by histochemical, immunohistochemical, immuno-ultrastructural, and organ bath techniques. NO synthase (NOS) I-III, the sGC alpha(2)-subunit/beta(1)-subunit, and cGMP were detected in odontoblasts and blood vessels. NOS I, sGC alpha(2), and cGMP were identified in nerve fibers. Treatment of rat molars with the NO donor NONOate (10(-5) M) increased cGMP staining intensities in blood vessels and odontoblasts, while NO synthase inhibitor L-NAME (10(-4) M) attenuated intensity of the reaction products for cGMP, suggesting an effect of endogenous NO on sGC. These correlations of patterns and alterations of cGMP staining intensities after treatment with the NO donor or NO inhibitor might represent an NO-sGC-cGMP signaling-dependent modulation of odontoblasts, blood vessels, and nerve fibers in the dentin-pulp complex.

Animals↗

PubMed2004

Nitric oxide, a key signaling molecule in the murine early embryonic heart.

Nitric oxide (NO) is thought to play an important role as a signaling molecule in embryonic and adult cardiomyocytes; however, its involvement in muscarinic signaling is still unclear. The aim of the present work was to analyze the muscarinic modulation of the L-type Ca2+ current (ICa) in early- and late-stage embryonic ventricular cardiomyocytes. Muscarinic stimulation depressed basal ICa by 30.1 +/- 3.2% (n=27) in early-stage cardiomyocytes. Pharmacological evidence suggested that the muscarinic modulation was mediated through generation of NO, activation of cGMP-dependent phosphodiesterase (PDE) 2, and ensuing lowering of cyclic AMP/protein kinase A (cAMP/PKA) levels. Conversely, in late-stage cardiomyocytes, muscarinic regulation of ICa occurred in a NO-independent manner via inhibition of prestimulated adenylyl cyclase (AC). To unequivocally prove the involvement of NO and to identify the nitric oxide synthase (NOS) isoform(s), we analyzed muscarinic signaling in embryonic ventricular cardiomyocytes of NOS2 (-/-) and NOS3 (-/-) mice. The early-stage NOS3 (-/-) cardiomyocytes lacked muscarinic modulation, whereas it was preserved in NOS2 (-/-) cells. Moreover, at the late embryonic stage, muscarinic modulation of ICa was intact in both strains. Thus, NO is the key regulator of muscarinic signaling in the early embryonic ventricle, whereas at later stages, signaling occurs through a NO-independent pathway.

Animals↗

PubMed2004

Implication of therapeutic cloning for organ transplantation.

Replacement of damaged myocardium with electrically functional, contracting syncytium with a balanced blood supply remains a key goal for the treatment of hearts damaged by coronary heart disease or other disorders. Stem cell therapy offers a potential solution. This paper describes the value of in vitro stem cell research to unravel the roles of key regulatory molecules in embryogenesis of myocardium and blood vessels. Studies have shown that functioning myocytes can be derived from stem cells in vitro and engrafted into infarcted areas of heart where they develop into functional adult like cardiomyocytes with action potentials and capacity for beta adrenergic and muscarinic regulation. Further studies have identified specific roles for platelet endothelial cell adhesion molecule (PECAM), vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF) in the sequential differentiation of blood vessels and capillaries.

Animals↗

PubMed2003

The preferential beta3-adrenoceptor agonist BRL 37344 increases force via beta1-/beta2-adrenoceptors and induces endothelial nitric oxide synthase via beta3-adrenoceptors in human atrial myocardium.

1 The present study investigated the effects of the preferential beta(3)-AR agonist BRL 37344 (BRL) on force of contraction (FOC), Ca(2+)-transient and eNOS-activity in human right atrial myocardium. 2 BRL concentration-dependently caused an increase in FOC that was paralleled by an increase in Ca(2+)-transient and a shortening of time to half peak relaxation (T0.5T). These effects were abolished in the presence of propranolol (0.3 micro M). 3 BRL acted as a competitive antagonist towards isoprenaline and in binding experiments it was shown to have a distinct affinity towards beta(1/2)-AR. 4 In immunohistochemical experiments BRL (10 micro M) increased detection of activated eNOS. This effect remained constant in the presence of propranolol (0.3 micro M). 5 BRL increased directly detected NO in DAF-staining experiments. This increase was significantly smaller in the presence of the NO-inhibitor L-NAME. 6 The inotropic effects of BRL were not changed in the presence of L-NMA. 7 These results suggest that the inotropic effects of BRL in human atrium are mediated via beta(1/2)-AR, whereas the increase of atrial eNOS-activity is due to beta(3)- adrenergic stimulation. This increase in eNOS-activity did not influence atrial myocardial contractility. In conclusion, this study shows that beta(3)-adrenergic stimulation is present in human atrium, but may not be functionally as significant as in the left ventricle.

Adrenergic beta-Agonists↗

PubMed2003

Morphology and density of initial lymphatics in human myocardium determined by immunohistochemistry.

BACKGROUND: Myocardial edema is a common finding in congestive heart failure, transplant rejection, and cardiomyopathy. Although pathological alterations in the lymphatic morphology are part of the underlying disease, knowledge on these changes is limited. However, lymphatic morphology may be investigated by immunohistochemical staining for fms-like tyrosine 4 kinase (flt-4), which is specific for lymphatic endothelium in adult tissue. METHODS: We used myocardial tissue of ventricular out flow tract taken from five human semilunar valves harvested as allografts but unsuitable for implantation for analysis, performing immunohistochemical staining for flt-4 with a commercially available antibody. Lymphatic morphometry was completed according Gundersen method. RESULTS: Immunohistochemical staining for flt-4 resulted in successful labeling of lymph capillaries in adult human myocardium. Lymph capillary density was calculated as 50.7 +/- 12.5 per mm2 and average diameter was 3.7 +/- 0.7 microm. Conclusions. Lymph capillary morphology in human myocardium may be successfully determined by immunohistochemical staining for flt-4. Tissue samples as small as myocardial biopsies may be used for analysis. Using this method, morphological changes in myocardial lymphatics may be investigated in various cardiovascular diseases.

Adult↗

PubMed2002

MAP kinase 1/2 (Erk 1/2) and serine/threonine specific protein kinase Akt/PKB expression and activity in the human corpus cavernosum.

Nitric oxide (NO) is an important mediator in the cavernosal smooth muscle relaxation that causes erections. The purpose of this study was to examine the existence, distribution and phosphorylation stage of two recently discovered key enzymes for NO regulation in human cavernosal tissue, the MAP Kinase 1/2 (Erk 1/2) and the serine/threonine specific protein kinase Akt/PKB. The expression of the enzymes was examined in corpus cavernosum specimens taken from both potent men and from patients with long-term impotence. There was a distinct difference in the activation stage of the MAP Kinase 1/2 (Erk 1/2) between endothelium and smooth muscle cells in potent patients. This finding gives evidence for a cell-type-specific regulation of the eNOS-dependent NO release. Furthermore, we found a higher basal level of active MAP Kinase 1/2 (Erk 1/2) in impotent patients. This finding gives the first evidence for an inhibitory influence of MAP Kinase 1/2 (Erk 1/2) on cavernosal eNOS activity.

Adolescent↗

PubMed2002

Epidemiology of Peyronie's disease.

Francois Gigot de la Peyronie, surgeon to Louis XV of France, has become synonymous with the rather enigmatic though not uncommon condition of Peyronie's disease (PD), a localized connective tissue disorder of the penile tunica albuginea. The true prevalence of Peyronie's disease is unknown. Therefore, we decided to perform an evaluation of existing epidemiological data. A prevalence rate of 3.2% was determined in male inhabitants of the greater Cologne area. This is much higher than revealed by the data reported up to now, thus rendering the accepted prevalence rates of 0.3% to 1% untenable. The actual prevalence of Peyronie's disease may be even higher, considering many patients' reluctance to report this embarrassing condition to their physicians. Along these lines, most clinicians note that the number of Peyronie's patients has increased since the advent of oral sildenafil. Comparably high prevalences are known for diabetes and urolithiasis, suggesting a greater frequency of this rare disease than formerly believed.

Age Distribution↗

PubMed2001

Nitric oxide synthase expression and function in embryonic and adult cardiomyocytes.

Nitric oxide (NO) is an important signalling molecule that plays a relevant role in different cell systems, among them the adult heart. The effects of NO are primarily mediated through modulation of Ca(2+) homeostasis, myofibrillar contractility, and metabolic regulation in cardiomyocytes. Recent evidence also suggests an important role of NO for cardiomyogenesis by modulating proliferation and differentiation and regulating cardiac function. In the embryonic, but also the healthy and diseased, adult mammalian heart, the inducible (iNOS) and the endothelial (eNOS) nitric oxide synthases (NOS) are detected. However, the expression pattern of NO and its function differ during development. Furthermore, under pathophysiological conditions NOS expression can also change and cause impairment of cardiac performance and cytotoxic effects. The present review focuses on the role and function of NO during cardiomyogenesis, the mechanisms responsible for eNOS availability, and the paracrine effects of NO generated by cardiomyocytes.

Animals↗

PubMed2001

Identification of the cardiac ryanodine receptor channel in membrane blebs of sarcoplasmic reticulum.

Blebs of the sarcoplasmic reticulum (SR) membrane of heart muscle cells were generated after saponin perforation of the plasma membrane followed by complete hypercontraction of the cell. Although characteristic proteins of the plasma membrane, namely the beta1-adrenoreceptor and Galphai, were stained by monoclonal antibodies in the hypercontracted cells, these proteins could not be detected in the adjacent blebs. Monoclonal antibodies to the cardiac ryanodine receptor (RyR2), calsequestrin and SERCA2 bound at different amounts to surface components of the blebs and to components of the hypercontracted cells. From the immunofluorescence signals we conclude that the blebs are mainly constituted of corbular and junctional SR membrane, and only to a lesser extent of network SR membrane. Deconvolution microscopy revealed that the membrane location of RyR2, calsequestrin and SERCA2 in the bleb is comparable to native SR membrane. At the bleb membrane giga-ohm seals could be obtained and patches could be excised in a way that single-channel currents could be measured, although these are not completely identified.

Animals↗

PubMed2001

Disruption of cytoskeletal integrity impairs Gi-mediated signaling due to displacement of Gi proteins.

beta1 integrins play a crucial role as cytoskeletal anchorage proteins. In this study, the coupling of the cytoskeleton and intracellular signaling pathways was investigated in beta1 integrin deficient (-/-) embryonic stem cells. Muscarinic inhibition of the L-type Ca2+ current (ICa) and activation of the acetylcholine-activated K+ current (IK,ACh) was found to be absent in beta1 integrin-/- cardiomyocytes. Conversely, beta adrenoceptor-mediated modulation of ICa was unaffected by the absence of beta1 integrins. This defect in muscarinic signaling was due to defective G protein coupling. This was supported by deconvolution microscopy, which demonstrated that Gi exhibited an atypical subcellular distribution in the beta1 integrin-/- cardiomyocytes. A critical role of the cytoskeleton was further demonstrated using cytochalasin D, which displaced Gi and impaired muscarinic signaling. We conclude that cytoskeletal integrity is required for correct localization and function of Gi-associated signaling microdomains.

Acetylcholine↗

PubMed2001

Nebivolol, carvedilol and metoprolol do not influence cardiac Ca(2+) sensitivity.

It has been argued that some beta-adrenoceptor antagonists may directly influence myofibrillar cross-bridge interaction in cardiac skinned fiber preparations of animal models. The present study investigates the effects of nebivolol, metoprolol and carvedilol on tension development of Triton X-100 skinned fibers obtained from human failing myocardium as well as on force of contraction and intracellular Ca(2+) transient in isolated trabeculae. In skinned fiber preparations, none of the beta-adrenoceptor antagonists (10 microM) influenced Ca(2+) sensitivity of tension development or maximal Ca(2+) activated tension (DT(max)): control: EC(50) for Ca(2+): 1.28+/-0.05 microM, DT(max): 14.09+/-0.59 mN/mm(2); nebivolol: 1.36+/-0.1 microM, 14.14+/-0.95 mN/mm(2); carvedilol: 1.32+/-0.11 microM, 13.83+/-0.90 mN/mm(2); metoprolol: 1.34+/-0.14 microM, 13.72+/-0.36 mN/mm(2). Simultaneous measurement of force and Ca(2+) transient in the presence of the beta-adrenoceptor antagonists (3 microM) showed that the decrease in force of contraction was paralleled by a similar decrease in the intracellular Ca(2+) transient. In conclusion, none of the investigated beta-adrenoceptor antagonists influenced Ca(2+) sensitivity of myofibrillar tension development in human failing myocardium.

Adrenergic beta-Antagonists↗