Contribution to the factors involved in the protective effect of ischemic preconditioning. The role of catecholamines and protein kinase C.
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Animals↗
Biomedical subjects
W Schaper
Publications and source records attributed to W Schaper.
Collateral vessel growth in the human heart. Role of fibroblast growth factor-2.
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Angina, Unstable↗
Characterization of differentially expressed genes following brief cardiac ischemia.
For the study of ischemia-related adaptations we employed DDRT-PCR on mRNA obtained from heart regions undergoing brief (10') occlusions/reperfusions. We found and sequenced 52 differentially expressed clones that we further characterized using Northern analysis with RNA from a wide variety of tissues. We selected only clones (1) with a new sequence, (2) that showed a Northern signal, and (3) that exhibited organ-specific (heart, muscle) or (4) situation-specific (ischemia, non-specific stress) expression. We found two new heart-specific transcripts and three new stress-inducible genes. The transcripts with known sequences showed an expression pattern typical for repair processes after ischemia-reperfusion (ubiquitin, ATPases). About 20% of clones were truly differentially expressed.
Animals↗
Effects of barbiturates on hypoxic cultures of brain derived microvascular endothelial cells.
An in vitro model of the blood-brain barrier (BBB) consisting of porcine brain derived microvascular endothelial cells (BMEC) seeded onto collagen-coated polycarbonate membranes was used to investigate the effects of the barbiturates, methohexital and thiopental, on permeability properties of the endothelial cell monolayer under hypoxia. The permeability of cultured BMEC to ions and sucrose increased significantly during 6 h of hypoxia in a reversible manner. Cells were resistant to hypoxia for up to 24 h, but 48 h resulted in marked damage as assessed by the release of lactate dehydrogenase activity into the culture medium. The hypoxia-induced increase of the permeability was unchanged in the presence of superoxide dismutase (SOD) and catalase. Methohexital and thiopental decreased the hypoxia-induced permeability increase in a concentration-dependent manner and permeability changes were abolished completely at the barbiturate concentration of 50 micrograms/ml. The barbiturates had no effect on the intracellular cAMP content which started to decline after 3 h of hypoxia. Results suggest that barbiturates at high concentrations might be able to prevent permeability changes of the BBB during cerebral ischemia.
Animals↗
The effect of angiotensin II on myosin heavy chain expression in cultured myocardial cells.
Angiotensin II (AII), the principal mediator of the renin-angiotensin system, is an important regulator of vascular and cardiac homeostasis. AII has also been shown to be a regulator of cardiac hypertrophy and of the corresponding changes in amount and composition of certain tissue proteins. We examined the trophic effects of AII on cultured myocytes derived from neonatal rat ventricles and followed, by Northern blot analysis and polyacrylamide gel electrophoresis, the expression of alpha- and beta-myosin heavy chain iso-mRNAs and isoproteins. Our findings show that a single administration of AII is sufficient to induce a trophic response in cultured beating myocytes and to enhance the expression of beta-myosin heavy chain iso-mRNA and isoprotein, having no effect on alpha-myosin heavy chain. Induction of alpha-myosin heavy chain expression by thyroid hormone before AII was administered showed that AII could not potentiate a shift from alpha- to beta-myosin heavy chain predominance. We suggest that the potency of AII to regulate the expression of myosin heavy chain isogenes is restricted to the beta isoform and is overridden by thyroid hormone.
Angiotensin II↗
Expression of adhesion molecules is specific and time-dependent in cytokine-stimulated endothelial cells in culture.
The time course of expression of the adhesion molecules E-selectin, VCAM-1, ICAM-1 and PECAM-1 was studied in interleukin-1 beta-stimulated human umbilical vein cells (HUVEC) and the subcellular sites of synthesis were determined by means of fluorescence immunohistochemistry. The maximal number of cells labelled for E-selectin was observed at 2-4 h, for VCAM-1 at 4-8 h and ICAM-1 at 6-72 h. At 8 h, E-selectin and VCAM-1 started to disappear, but ICAM-1-positive cells persisted. PECAM-1 was constitutively expressed. De novo synthesis for E-selectin started at 1 h and for both, VCAM-1 and ICAM-1 at 1.5-2 h. Maximal synthetic activity was observed at 2.5-4 h for E-selectin and at 4-6 h for VCAM-1 and ICAM-1; thereafter, synthesis slowly decreased. Transport granules occurred at 1.5 h for E-selectin and 4 h for VCAM-1; they were absent for ICAM-1. Diffuse cellular and membrane labelling indicative of the functional activity of the adhesion molecules began at 2-4 h for E-selectin, and 4 h for VCAM, but was constitutively present for ICAM-1. In conclusion, each adhesion molecule shows a specific time-dependent course of appearance and disappearance in interleukin-1 beta-stimulated HUVECs in accordance with their physiological role in vivo. These morphological results confirm data obtained by flow cytometry and Western blotting, but they provide new information about the behaviour of individual cells with regard to the sites of synthesis and cellular localization of the adhesion molecules.
Antigens, Differentiation, Myelomonocytic↗
Myocyte degeneration and cell death in hibernating human myocardium.
OBJECTIVES: The aim of this study was to analyze the morphologic characteristics of myocyte degeneration leading to replacement fibrosis in hibernating myocardium by use of electron microscopy and immunohistochemical techniques. BACKGROUND: Data on the ultrastructure and the cytoskeleton of cardiomyocytes in myocardial hibernation are scarce. Incomplete or delayed functional recovery might be due to variable degree of cardiomyocyte degeneration in hibernating myocardium. METHODS: In 24 patients, regional wall motion abnormalities were analyzed by use of the centerline method before and 6 +/- 1 months after coronary artery bypass surgery. Preoperative technetium-99m sestamibi uptake was measured by single-photon emission computed tomography for assessing regional perfusion. Fluorine-18 fluorodeoxyglucose uptake was measured by positron emission tomography to assess glucose metabolism. Transmural biopsy specimens were taken during coronary artery bypass surgery from the center of the hypocontractile area of the anterior wall. RESULTS: The myocytes showed varying signs of mild-to-severe degenerative changes and an increased degree of fibrosis. Immunohistochemical analysis demonstrated disruption of the cytoskeletal proteins titin and alpha-actinin. Electron microscopy of the cell organelles and immunohistochemical analysis of the cytoskeleton showed a similarity in the degree of degenerative alterations. Group 1 (n = 11) represented patients with only minor structural alterations, whereas group 2 (n = 13) showed severe morphologic degenerative changes. Wall motion abnormalities showed postoperative improvements, and nuclear imaging revealed a perfusion-metabolism mismatch without significant differences between the groups. CONCLUSIONS: Long-term hypoperfusion causes different degrees of morphologic alterations leading to degeneration. Preoperative analysis of regional contractility and perfusion-metabolism imaging does not distinguish the severity of morphologic alterations nor the functional outcome after revascularization. The insufficient act of self-preservation in hibernating myocardium may lead to a progressive structural degeneration with an incomplete and delayed recovery of function after restoration of blood flow.
Adult↗
Therapeutic targets in cardiovascular disorders.
The feasibility of gene therapy for cardiovascular diseases related to atherosclerosis is a topic that needs to be addressed. Most recent papers have dealt with technical aspects and feasibility and most of the genes transferred were reporter genes like those for beta-galactosidase or luciferase. This may mean that the ideal vector, one that is not pathogenic or immunotolerant but is still efficient, is still not available. The results of these studies are ambiguous and it has been doubted whether the genes targeted really affect the disease. Further efforts are therefore needed to elucidate the underlying pathophysiology.
Animals↗
The international rank order of clinical cardiology.
A cardiological ranking list was prepared based on papers published in 1981-1992. The nations studied comprised the G-7 countries, Belgium, Denmark, Finland, the Netherlands, Norway, Sweden and Switzerland. The number of citations received by these publications was checked. In general the output and citation frequency in the last decade increased, although often temporarily. These data were also related to population size and expenditure on research and development. They show that the United States leads research in clinical cardiology. In most G-7 nations, however, the quality and quantity of cardiological publications lag behind those of the smaller West-European countries. This may be partly due to differences in funding and/or publication in a language other than English.
Cardiology↗
Molecular mechanisms of coronary collateral vessel growth.
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Collateral Circulation↗
Preparation of miniprep-DNA for automated non-radioactive sequencing.
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Sequence Analysis, DNA↗
-Myocardial protection by preconditioning. Experimental and clinical significance-.
Short periods of ischemia render the myocardium more resistant to a subsequent prolonged coronary occlusion resulting in a reduction of infarct size. This cardioprotective mechanism has been called ischemic preconditioning. Acute myocardial ischemia results in a rapid decline of high energy phosphates. After short periods of ischemia the high energy phosphate levels are better preserved and the increase of lactate is slower during the prolonged subsequent ischemia in the preconditioned group compared to control. The duration of ischemia needed for induction of the protective effect is 2.5 min in dogs and 20 min in our swine model. In porcine myocardium the protection is lost about 1 h after induction and a renewal is not possible at that time, but is 24 h later. For rabbits or dogs, but not in pigs, a late protection 24 h after induction or preconditioning has been shown ("second window of protection"). Adenosine or adenosine A1 receptor agonists, muscarinic M2 receptor agonists, alpha 1-receptor agonists and bradykinin B2 receptor agonists as well as opening of the K+ATP-channel substitute for ischemia in the induction of protection. Activation of protein kinase C results in protection in rats and rabbits, but not in dogs or pigs. Inhibition of protein kinase C translocation or kinase activity results in a loss of the protection induced by preceding ischemia. After blockade of the K+ATP-channel the protection induced by adenosine A1 receptor activation is lost. Therefore opening of the K+ATP-channel is a prerequisite for induction of the protective effect. Inhibition of the inhibitory G-protein by pertussis toxin has been shown to result in a loss of protection, therefore the Gi-protein seems to be involved in the evolution of protection. In humans during coronary angioplasty anginal pain and lactate production during a second balloon occlusion is diminished without any change in the regional myocardial perfusion. This adaptation is inhibited by blockade of the K+ATP-channel or of the adenosine A1 receptor. Intermittent cross-clamping before a longer occlusion during open-heart surgery results in a better preservation of high energy phosphates compared to controls without preceding short ischemia. These observations support the hypothesis that ischemic preconditioning also occurs in humans. Angina pectoris preceding the myocardial infarction may have preconditioned the human heart against the subsequent myocardial infarction, but studies concerning the influence of angina pectoris on short-term outcome after thrombolysis are conflicting. In the future, ischemic preconditioning or preconditioning with drugs may prolong the duration of ischemia tolerated without necrosis and improve the prognosis of patients by reducing the infarct size.
Adenosine Triphosphate↗
[The role of adenosine in "ischemic preconditioning"].
Repeated short coronary occlusions trigger probably more than one pathway leading to increased tolerance toward ischemia. Adenosine plays probably a very important but not an exclusive role. It may act via opening of A1-receptor-operated K(+)-channels that lead to hyperpolarization of the cell, and it has antiadrenergic actions. A proposed action of adenosine via protein kinase C is not confirmed. Trophic factors are expressed during short periods of ischemia and contribute to survival, probably via inhibition of apoptosis.
Adenosine↗
Altered gene transcription following brief episodes of coronary occlusions.
This study was designed to elucidate whether previously observed enhanced mRNAs were due to accelerated transcription, enhanced mRNA stability or both mechanisms. We employed the nuclear run-on technique on myocardial nuclei and found the transcriptional induction of several genes, especially nuclear protooncogenes, Ca2+ regulating and heat shock protein genes.
Animals↗
Molecular manifestations of cardiac hypertrophy in the spontaneously hypertensive rat effects of antihypertensive treatments.
Antihypertensive treatments were given to young and adult SHRs, to prevent and reverse hypertension, respectively. Cardiac hypertrophy and the steady state level of the "fetal" genes, ANP, alpha-skeletal actin (alpha-skA), and beta myosin heavy chain (beta-MHC) mRNAs were assessed. Our findings show that the reduction of blood pressure does not consistently result in a similar regression of the "fetal gene program".
Actins↗
Expression of vascular permeability factor/vascular endothelial growth factor in pig cerebral microvascular endothelial cells and its upregulation by adenosine.
Porcine brain-derived microvascular endothelial cells (BMEC) express the mRNA of the polypeptide mitogen vascular permeability factor/vascular endothelial growth factor (VPF/VEGF). The VEGF mRNA expression in BMEC could be upregulated 2.5 fold after 6 h of treatment with 5 microM adenosine and adenosine agonists. Adenosine A1 and A2 receptor antagonists completely abolished the upregulation of the VEGF mRNA caused by adenosine. Agents like forskolin and cAMP phosphodiesterase inhibitors which are known to increase the cAMP level decreased the VEGF mRNA expression slightly whereas agents like phorbolester which activate the proteinkinase C (PKC) pathway enhanced the VEGF mRNA expression 3.2 fold. The specific inhibitor of the PKC bisindolymaleimide (BIM) abolished the upregulation of the VEGF mRNA by adenosine completely. The BMEC conditioned medium stimulated the proliferation of BMEC itself and Western blot analysis of the BMEC conditioned medium using a polyclonal antibody to human VEGF showed one band at 18 kDa which was slightly upregulated after treatment with adenosine. Results suggest that the effect of adenosine on the VEGF mRNA expression is mediated via the A1 receptor and that an activation of the PKC may be involved in the observed effects of adenosine on the VEGF mRNA expression. VEGF produced by BMEC and which is inducible by adenosine may function via the autocrine pathway and may be involved in repair reactions of brain blood vessels and/or the maintenance of these cells.
Adenosine↗
A novel heart derived inhibitor of vascular cell proliferation. Purification and biological activity.
Recently, growth factors with mitogenic properties for vascular wall cells have been isolated from adult heart tissue. Since angiogenesis in the heart typically does not occur under normal physiological conditions, despite the presence of many growth factors, we hypothesized the existence of growth inhibitors. To test this hypothesis, we subjected whole bovine heart extracts to a series of protein purification steps in search of such an inhibitor. The purification procedure consisted of ammonium sulfate precipitation followed by cation exchange chromatography, hydroxylapatite chromatography, ultrafiltration and gelfiltration. We isolated a small protein, which is an inhibitor of cell proliferation from the bovine heart. The inhibitor reversibly suppressed [3H]-thymidine incorporation into nuclei of bovine aortic endothelial and smooth muscle cells. The moiety responsible for the inhibitory activity was identified biochemically (SDS Page, isoelectric focusing, HPEC) as an 11 kD protein with an isoelectric point of 7. The substance is a heat and acetic acid stable protein which does not bind to reversed phase columns because of its hydrophilic character. The inhibitor has no affinity to heparin sepharose. The inhibitory activity was destroyed by hydrolysis. No homology to any hitherto structurally investigated growth inhibitor was observed using the chemical determination of the amino acid sequence by microsequencing after previous trypsin digestion. We conclude that the described growth inhibitor may counteract the activity of mitogens that are abundantly present in normal heart. Vascular cell proliferation may be regulated by inhibition or production of the inhibitor.
Amino Acid Sequence↗
Control of coronary angiogenesis.
We investigated the development of coronary collaterals in canine and porcine models using either progressive experimental coronary occlusion or microembolism of small vessels. Muscular arteries developed on the epicardial surface of canine--but not of porcine hearts, where large, thin-walled intra-myocardial capillaries developed irrespective of the type of vascular occlusion. The common motif for both types of vascular adaptation is the part played by inflammation, i.e. the involvement of monocytes/macrophages that are probably the producers of growth factors. Emphasis is placed on the importance of remodelling by controlled proteolysis to create the space for the new vascular cells.
Animals↗