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N Frey

Publications and source records attributed to N Frey.

36 records · Page 2Linked to original sources
PubMed1997

Transgenic animal models: new avenues in cardiovascular physiology.

Application of molecular genetic tools to inherited cardiovascular disorders has provided important insights into the molecular mechanisms underlying cardiomyopathies, arrhythmias, blood pressure regulation, and atherosclerosis. In addition, alteration of gene expression has been observed under common cardiovascular conditions such as cardiac hypertrophy and heart failure. Recent advances in transgenic and gene-targeting approaches allow a sophisticated manipulation of the mouse genome by gene addition, gene deletion, or gene modifications. These transgenic models enable the dissection of in vivo pathways responsible for these complex disease phenotypes. This review describes tissue-specific promoters suitable for targeting candidate genes to the cardiovascular system as well as a number of valuable transgenic animal models of blood pressure regulation, atherogenesis, defects in the coagulation system, cardiac hypertrophy, myocarditis, cardiomyopathies, and heart failure. Limitations and difficulties associated with these transgenic approaches are discussed. Animal models which may provide a basis for future gene therapy of cardiovascular diseases are introduced. Finally, methods are described to regulate the spatial and temporal expression level of a transgene, to inactivate a target gene in a tissue-specific manner, and to introduce specific mutations into the genome. These recent advances in transgenic technology are expected to have a considerable impact on cardiovascular research in the near future.

Animals↗
PubMed1997

Analysis of tissue-specific gene delivery by recombinant adenoviruses containing cardiac-specific promoters.

OBJECTIVE: To approach heart muscle diseases by gene transfer, an adenoviral vector system was intended to be established suitable for gene expression in ventricular and/or atrial myocardium. METHODS: Two adenoviral vectors (Ad-mhcLuc, Ad-mlcLuc) were constructed, in which the luciferase reporter gene is under control of either the ventricle-specific myosin light chain-2 (mlc-2v) or the atrial- and ventricular-specific alpha-myosin heavy chain (alpha-mhc) promoter. For controls, a recombinant adenovirus without promoter (Ad-Luc) and one with the Rous sarcoma virus (rsv) promoter (Ad-rsvLuc) were generated. A volume of 20 microliters containing 2 x 10(9) plaque forming units (pfu) of the recombinant adenoviruses Ad-mhcLuc, Ad-mlcLuc, Ad-rsvLuc or Ad-Luc was injected into the cardiac cavity or the quadriceps femoris muscle of neonatal rats. After five days animals were sacrificed and nine different tissues were analyzed for reporter gene expression by detection of light activity relative to mg of tissue. RESULTS: Injections of recombinant adenoviruses into the cardiac cavity of neonatal rats resulted in heart-specific gene expression of Ad-mlcLuc (20 fold of Ad-Luc; 11% of Ad-rsvLuc), whereas Ad-mhcLuc gave mainly luciferase activity in the heart (6.5-fold of Ad-Luc; 3% of Ad-rsvLuc) with additional activity in lung and liver (2-4 fold of Ad-Luc). In the ventricular tissue Ad-mlcLuc revealed a 35-fold higher luciferase activity, whereas Ad-mhcLuc, Ad-rsvLuc and Ad-Luc showed only 2-fold higher luciferase activities compared to the atrium. Viral DNA in atrial and ventricular tissue was detected by PCR at approximately the same abundance independent of the injected type of adenovirus. Direct injection of Ad-mhcLuc and Ad-mlcLuc into the thigh muscle revealed only background luciferase activities. CONCLUSIONS: In the adenoviral system only the mlc-2v promoter may fulfil the safety requirements for a myocardial specific gene expression with a high selectivity for the ventricular myocardium, thus providing a promising tool for future gene therapy of cardiomyopathies.

Adenoviridae↗
PubMed1995

Molecular mimicry in halothane hepatitis: biochemical and structural characterization of lipoylated autoantigens.

Exposure of human individuals to halothane causes, in about 20% of all cases, a mild transient form of hepatotoxicity. A small subset of exposed individuals, however, develops a potentially severe and life-threatening form of hepatic damage, coined halothane hepatitis. Halothane hepatitis is thought to have an immunological basis. Sera of afflicted individuals contain a wide variety of autoantibodies against hepatic proteins, in both trifluoroacetylated form (CF3CO-proteins) and, at least in part, in native form. CF3CO-proteins are elicited in the course of oxidative biotransformation of halothane, and include the trifluoroacetylated forms of protein disulfide isomerase, microsomal carboxylesterase, calreticulin, ERp72, GRP 78, and ERp99. Current evidence suggests that CF3CO-proteins arise in all halothane-exposed individuals; however, the vast majority of individuals appear to immunochemically tolerate CF3CO-proteins. The lack of immunological responsiveness of these individuals towards CF3CO-proteins might be due to tolerance, induced through the occurrence of structures in the repertoire of self-determinants, which immunochemically and structurally mimic CF3CO-proteins very closely. In fact, lipoic acid, the prosthetic group of the constitutively expressed E2 subunits of the family of mammalian 2-oxoacid dehydrogenase complexes and of protein X, was shown by immunochemical and molecular modelling analysis to be a perfect structural mimic of N6-trifluoroacetyl-L-lysine (CF3 CO-Lys), the major haptenic group of CF3CO-proteins. As a consequence of molecular mimicry, autoantibodies in patients' sera not only recognize CF3CO-proteins, but also the E2 subunit proteins of the 2-oxoacid dehydrogenase complexes and protein X, as autoantigens associated with halothane hepatitis. Furthermore, a fraction of patients with halothane hepatitis exhibit irregularities in the hepatic expression levels of these native, not trifluoroacetylated autoantigens. Collectively, these data suggest that molecular mimicry of CF3CO-Lys by lipoic acid, or the impairment thereof, might play a role in the susceptibility of individuals for the development of halothane hepatitis.

Autoantigens↗
PubMed1995

[A transgenic animal model: new possibilities for cardiovascular research].

By means of molecular biology and genetic research the influence of genetic factors on a great variety of human diseases could be shown. In the field of cardiovascular research the genetic defects of a few monogenetic disorders, such as Marfan's syndrome and hypertrophic cardiomyopathy, have been characterized. In addition, candidate genes for polygenetic diseases, such as arterial hypertension and atherosclerosis, have been cloned. However, the identification of a candidate gene or its mutation does not prove its influence on the phenotype or the final cause of a particular disease. Only a targeted manipulation of a defined candidate gene in a transgenic animal model helps to understand the role of the gene and its product in the whole organism. Transgenic experiments can be divided into gene-addition and gene-deletion models. In a gene-addition experiment a fusiongene is microinjected into a fertilized oocyte. The fusiongene itself consists at least of a regulatory element promoter and of a DNA sequence coding for the gene product (protein) of intended overproduction. The choice of the right promoter is important for obtaining tissue-specific gene expression. The cardiac myosin light chain-2 promoter for example leads to a ventricle-specific gene expression in cardiomyocytes from early embryogenesis through adulthood. In a gene-deletion experiment on the other hand, the target gene is selectively knocked out by homologous recombination in embryonic stem (ES) cells. The selected ES-cells are then injected into blastocysts. If the ES-cells are integrated into the germ line and transmitted to the progeny, a transgenic line is established. This review article describes planning and development of transgenic animals and discusses established transgenic animal model systems with regard to cardiovascular physiology. In addition, animal models which may provide a basis for future gene therapy will be introduced.

Animals↗
PubMed1995

[Clinical aspects and follow-up in dilated cardiomyopathy].

Dilative cardiomyopathy is a heterogeneous myocardial disease characterized by a depressed contractile function and ventricular dilation. The exercise intolerance of patients with dilative cardiomyopathy is partly explained by changes of metabolism and composition of skeletal muscle, whereas the physical findings result from progressive heart failure and cardiac remodeling. The clinical course of the disease is highly variable and prognostic indicators of progressive heart failure or cardiac arrhythmias are of little value in the assessment of cardiac risk in an individual patient. During recent years the mortality of patients with dilative cardiomyopathy was 5-15%, which appears to be lower than previously reported. The differences in mortality today and in previous years may be explained by a more precise and earlier diagnosis of the disease and possibly better treatment strategies. Patients with a severely depressed left ventricular function but a stable clinical course, a good hemodynamic response to therapy, and an oxygen uptake of > 12 ml/kg min can be followed without heart transplantation. It can be expected that the definition of the molecular causes of dilative cardiomyopathy will lead to a better classification of the patients and the development of more efficient treatment strategies.

Cardiomyopathy, Dilated↗
PubMed1992

Potentiation of cardiodepressive action among calcium antagonists from different classes: evidence for a mechanism at the single calcium channel level.

The ability of calcium antagonists and antiarrhythmic agents to potentiate the negative inotropic effects of calcium antagonists was investigated in guinea-pig left atria. The potency of nitrendipine was enhanced by several amphiphilic agents by one order of magnitude or more (by pretreatment with quinidine or bepridil). The effect of preincubation with bepridil was investigated for a larger number of dihydropyridines. Only some of them were potentiated like nitrendipine. There was no potentiation between any two members of the same chemical group, i.e. between two dihydropyridines or two catamphiphilic calcium antagonists. The interaction between bepridil and nitrendipine was studied in more detail. In atria, its extent was influenced by several conditions, such as the stimulus frequency, the incubation temperature, or the extracellular K+ concentration. In measurements of whole-cell calcium currents in guinea-pig myocytes, the interaction was found to take place in a quantitatively similar manner. At the single channel level, an enhancement of the effects could also be demonstrated. It appears here that both drugs interact by binding to the same channel molecule. We conclude that the interaction may be due to 1.: an amphiphilic drug (like bepridil) binding to the channel very transiently and thus briefly favouring the inactivated channel state, which means that 2.: the other drug (like nitrendipine) has a higher chance to be bound because of its high affinity towards inactivated channels. Alternative explanations are also discussed.

Animals↗
PubMed1986

Rabbit corneal endothelial physiologic and morphologic characteristics following storage in MK medium and K-Sol.

Rabbit corneas were stored for 3, 7, 10 or 14 days in MK medium or K-Sol. Corneas were thinner immediately following removal from K-Sol than following removal from MK medium at all time periods studied. Following 3 days of storage, corneas stored in both solutions showed similar temperature reversal characteristics. Corneas stored for 7 and 10 days in MK medium also temperature reversed, whereas those stored in K-Sol did not. Corneas stored for 14 days in both solutions swelled following mounting in the specular microscope. Endothelial cell morphology was similar following storage in MK medium and K-Sol at all time periods studied. It is postulated that a persistant osmotic gradient is present across the endothelium following storage in K-Sol. This osmotic gradient occurs because of retention of chondroitin sulphate in the corneal stroma thereby preventing early temperature reversal.

Animals↗
PubMed1977

[Non-invasive determination of cardiac pump function by respiratory gas exchange measurement during submaximal exercise -- comparison with hemodynamic (heart catheterisation) data (author's transl)].

The continuous measurement of respiratory gas exchange under linearly increasing work load allows a relatively exact and reproducible localization of the point of rise of the ventilatory equivalent for oxygen (ASV). On the basis of the values of oxygen consumption (V(O2)(ASV)), oxygen pulse (O2-pulse(asv)) and relative ventilatory equivalent (Vetn. Equivalent(asv)/V(O2(ASV)), measured at the point ASV, it is possible to divide patients with different severity of heart disease into 4 groups of cardiac response to exercise: group I = normal, group II = diminished, group III = definitely limited and group IV = severely limited cardiocirculatory capacity. Simultaneous cardiac output measurements (thermodilution method) as well as the comparison with hemodynamic and angiographic data acquired during separate heart catheterization reveal good correlations between V(O2(ASV) and O2-pulse(asv) on the one hand and exercise values of cardiac output and stroke volume on the other (r = 0.82). Consequently, definite relations exist between the absolute ASV values as well as the group classification (I--IV) based on these and further heart catheterization data such as left bentricular (LV) enddiastolic pressure, LV ejection fraction, contraction pattern of the left ventricle and coronary angiogram respectively. The described method of measuring respiratory gas exchange under submaximal unsteady state bicycle exercise represents a reliable and rapid non-invasive stress test of cardiac pump function without putting too much strain on the heart patient as is frequently the case with the more familiar steady state (maximal) tests.

Cardiac Catheterization↗
PubMedDate not supplied

The lipoic acid containing components of the 2-oxoacid dehydrogenase complexes mimic trifluoroacetylated proteins and are autoantigens associated with halothane hepatitis.

Anti-CF3CO antibodies, monospecific toward trifluoroacetylated proteins (CF3CO-proteins), which are elicited in experimental animals and humans exposed to the anesthetic agent halothane, cross-react with an unknown protein of approximately 52 kDa, constitutively expressed in tissues of experimental animals and humans not previously exposed to the agent. Using anti-CF3CO antibody, the protein(s) of 52 kDa could be immunoprecipitated from solubilized rat heart homogenate. Two-dimensional gel electrophoretic analysis revealed the presence of distinct major (P1, P2) and minor (P3, P4, P5) protein components with apparent molecular masses of 52 kDa. From each of the components P1 and P2, the amino acid sequences of three peptides were determined and found to exhibit 100% identity with the corresponding amino acid sequences of the E2 subunit of the rat 2-oxoglutarate dehydrogenase complex (OGDC). Additionally to the E2 subunit of OGDC, anti-CF3CO antibody also recognized on immunoblots the purified E2 subunit of the branched chain 2-oxoacid dehydrogenase complex (BCOADC) and protein X, a constituent of the pyruvate dehydrogenase complex (PDC), in a manner sensitive to competition by N6-(trifluoroacetyl)-L-lysine (CF3CO-Lys), 6(RS)-lipoic acid, and N6-(6(RS)-lipoyl)-L-lysine (lipoyl-Lys). Furthermore, a discrete population of autoantibodies was identified in sera of patients with halothane hepatitis which could not discriminate between the lipoylated target epitope present on the E2 subunit of OGDC and epitopes on CF3CO-RSA, used as model for CF3CO-proteins. These data suggest that the autoantigenicity of these proteins in halothane hepatitis is based on the molecular mimicry of CF3CO-Lys by lipoic acid, the prosthetic group common to protein X and the E2 subunits of OGDC and BCOADC.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
PubMedDate not supplied

Risk stratification and therapeutic decision making in patients with acute coronary syndrome--the role of cardiac troponin T.

Patients with chest pain represent an inhomogeneous group with greatly varying severity of coronary artery disease and cardiac risk. The proper selection of different treatment strategies in these patients requires reliable risk assessment. Patients with definitive myocardial infarction: in patients with ST-segment elevation on ECG, a positive troponin T (cTnT) on admission identifies a group of patients having a threefold higher mortality rate than patients with a negative cTnT test. The differences in risk based on cTnT are found for patients treated with thrombolytic as well as mechanical recanalization therapy. These differences in mortality based on admission cTnT may be explained by more severe coronary artery disease, worse left ventricular function, and less efficient microvascular reperfusion in the cTnT-positive patients. Patients with rest angina: in patients with angina at rest, a positive cTnT value on admission identifies a subgroup having a threefold higher cardiac event rate than cTnT-negative patients. The cTnT-positive patients seem to benefit from treatment with low molecular weight heparin and fibrinogen receptor antagonists, while cTnT-negative patients do not. The differences in risk and response to therapy may be due to more severe coronary artery disease, more critical coronary artery stenoses, and a higher rate of intracoronary thrombus formation in the cTnT-positive versus negative patients. Low risk chest pain patients: in low risk chest pain patients, (i.e. no rest angina, no ECG-changes) cTnT-positive patients on admission have a twofold higher cardiac event rate than cTnT-negative patients. The proper treatment strategy for the low risk cTnT-positive patients remains to be determined. Troponin T versus troponin 1: many of the findings on cTnT also relate to troponin I. However, there is a high interassay variability of troponin I assays, which has to be taken into consideration.

Angina Pectoris↗