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T Rother

Publications and source records attributed to T Rother.

At least 19 recordsLinked to original sources
PubMed2001

Light scattering on hexagonal ice columns.

Light scattering on finite dielectric cylinders having noncircular cross sections has become of growing importance in remote-sensing applications. For analyzing their scattering characteristics at moderate size parameters, i.e., at a region where ray-tracing techniques fail, a few methods have been developed, among which an approximation based on the generalized separation-of-variables method has become very successful. This approach reveals two interesting features, which we discuss, that reduce the numerical effort drastically if applied to hexagonal (in general, 2n-periodic) boundary surfaces. Finally, some results for the phase function of hexagonal ice columns are given.

Journal Article↗
PubMed2000

[Fractional flow reserve as a deciding criterion for intervention in patients with 50% coronary stenoses and impaired myocardial perfusion].

BACKGROUND: A fractional flow reserve (FFRmyo) < 0.75 is a well validated parameter for significance of coronary stenoses in cases of normal myocardial function. We used the FFRmyo limit in patients with impaired myocardial perfusion by myocardial infarction and/or hypertension for intermediate stenoses of the LAD for decision to PTCA and checked the indication by clinical follow-up. METHODS: In 20 pts (5 women) with chest pain and visual 50 D% LAD stenoses, the FFRmyo was obtained by using a RADI-Pressure-Wire, the CFR by a densitometric technique (HODGSON), and the geometry of stenosis (minimal lumen diameter and diameter stenosis) by quantitative coronary angiography (QCA). EF and the kinetics of the anterolateral wall (expressed as radial shortening fraction) were measured by laevography. RESULTS: The mean age of our 20 pts. was 59.4 years: 13 of the pts. (65%) had a history of hypertension, 9 (45%) pts. a history of myocardial infarction. The mean diameter stenosis was 50.8%. The mean value of CFR was 2.9. The FFRmyo ranged from 0.66 to 0.90, the mean value was 0.78. The 12 pts. with FFRmyo > or = 0.75 (60%, group A) were treated with the usual anti-anginal medications. A PTCA was performed only in patients with FFRmyo < 0.75 (N = 8 (40%), group B). Except for one pt. with instent restenosis, in the 7 pts. with denovo stenoses stent implantation was performed. Significant differences between the groups A and B were seen only for the total number of myocardial infarctions (8/12 vs. 1/8) and diameter stenosis (48.5% vs. 54.3%). All lesions of group B had a diameter stenosis of 50% or higher. CFR correlated significantly with the radial shortening fraction (r = 0.75), minimal lumen diameter (r = -0.51) and diameter stenosis (r = -0.46). FFRmyo correlated with diameter stenosis (r = -0.47) only. All pts. treated with PTCA were primarily free of pain or reduced angina at least 1 CCS stage; only one developed an angina due to a restenosis (74 D%) 2 months after PTCA and stent implantation. The pts. of group A did not get worse, nor were they readmitted within 6 to 13 months after catheterization. CONCLUSIONS: Pts. with 50 D% stenoses, impaired myocardial perfusion and FFRmyo < 0.75 had a good long-term benefit concerning clinical and angiographic result. No pts. with FFRmyo < 0.75 had a D% lower than 50; therefore, the PTCA of intermediate stenoses without quantification must be avoided. CFR is not helpful for a decision to PTCA in such cases, because a normal value of CFR is relevant only.

Aged↗
PubMed2000

[Catheter ablation of supraventricular tachyarrhythmias].

The term "supraventricular tachyarrhythmia" summarizes electrophysiologically different arrhythmias. After detection of the mechanism of the present arrhythmia, the weak part of the reentrant circuit has to be identified using different mapping techniques. The catheter ablation is widely used as focal ablation (sinus tachycardia, ectopic atrial tachycardia, focal atrial fibrillation) or for interruption of conducting pathways (accessory pathways, AV nodal reentrant tachycardia). A single ablation line should be created in isthmus-dependent atrial flutter or in incisional tachycardias, which is less used now-a-days. Multiple ablation lines are needed for ablation of atrial fibrillation, which is a method investigated in arrhythmia centers only. Some arrhythmias are less well understood, not localizable and therefore not curatively treated with ablation techniques. Newer three-dimensional mapping methods may help in this situation. The challenge at the present time is the catheter ablation of atrial fibrillation.

Catheter Ablation↗
PubMed2000

Radiofrequency ablation of atrioventricular nodal reentrant tachycardia: mechanisms and recurrence rate.

Radiofrequency catheter ablation is the treatment of choice in atrioventricular nodal reentrant tachycardia. Electrophysiologic investigations in 623 patients revealed eight mechanisms of tachycardia ablation: Ablation of fast (I) or slow (II), modification of fast (III) or slow AV nodal pathways (IV), modification of both pathways (V), ablation of fast and modification of slow (VI), ablation of slow and modification of fast pathways (VII) and ablation of both pathways (VIII). The criteria of diagnosis of these eight mechanisms of tachycardia ablation are described. Follow-up showed fewer relapses in patients with ablation (0-2%) in comparison to patients with modification of a single AV nodal pathway (8-12%). Alteration of both pathways includes an increasing risk of total AV nodal block, which occurred in 7 patients (1.1%). Detailed analysis of the mechanism of catheter ablation is recommended in all patients after radiofrequency current delivery for AV nodal reentrant tachycardia to estimate the risk of relapse during follow-up or development of total AV block in the particular patient in case of a further ablation procedure.

Catheter Ablation↗
PubMed1999

Network of characterizing functions for stationary populations.

A variety of open systems in nature and society exist under dynamic equilibrium, maintained by statistical counterbalance between the entering and leaving of individuals and the stationarity of the exchange processes. A network of functions characterizing the dynamics of such a stationary population is established and discussed, which allows the mutual transference of system properties without the need of any explicit information about the microdynamic processes. In order to illustrate the potential benefit of these interdependence relations, examples taken from diverse branches of research (adsorption and reaction kinetics, demographic analysis, and coronary blood flow diagnosis) are given.

Journal Article↗
PubMed1998

Overexpression of the sarcolemmal calcium pump in the myocardium of transgenic rats.

The plasma membrane calmodulin-dependent calcium ATPase (PMCA) is a calcium-extruding enzyme controlling Ca2+ homeostasis in nonexcitable cells. However, its function in the myocardium is unclear because of the presence of the Na+/Ca2+ exchanger. We approached the question of the physiological function of the calcium pump using a transgenic "gain of function" model. Transgenic rat lines carrying the human PMCA 4 cDNA under control of the ventricle-specific myosin light chain-2 promoter were established, and expression in the myocardium was ascertained at the mRNA, protein, and functional levels. In vivo hemodynamic measurements in adult homozygous animals showed no differences in baseline and increased cardiac performance recruited by volume overload compared with controls. No differences between transgenic and control cardiomyocytes were found in patch clamp voltage dependence, activation/inactivation behavior of the L-type Ca2+ current, or fast [Ca2+]i transients (assessed by the Fura-2 method). To test whether the PMCA might be involved in processes other than beat-to-beat regulation of contraction/relaxation, we compared growth processes of neonatal transgenic and control cardiomyocytes. A 1.6- and 2.3-fold higher synthesis rate of total protein was seen in cells from transgenic animals compared with controls on incubation with 2% FCS for 24 hours and 36 hours, respectively. An effect of similar magnitude was observed using 20 micromol/L phenylephrine. A 1.4-fold- and 2.0-fold-higher protein synthesis peak was seen in PMCA-overexpressing cardiomyocytes after stimulation with isoproterenol for 12 hours and 24 hours, respectively. Because pivotal parts of the alpha- and beta-adrenergic signal transduction pathways recently have been localized to caveolae, we tested the hypothesis that the PMCA might alter the amplitude of alpha- and beta-adrenergic growth signals by virtue of its localization in caveolae. Biochemical as well as immunocytochemical studies suggested that the PMCA in large part was colocalized with caveolin 3 in caveolae of cardiomyocytes. These results indicate that the sarcolemmal Ca2+-pump has little relevance for beat-to-beat regulation of contraction/relaxation in adult animals but likely plays a role in regulating myocardial growth, possibly through modulation of caveolar signal transduction.

Animals↗
PubMed1995

[First experiences with electron beam computed tomography of the heart:comparison with heart catheterization and echocardiographic findings].

AIM: To evaluate the diagnostic value of ultrafast CT in comparison to established methods in cardiology. MATERIAL AND METHODS: Cine and flow studies were performed in 30 patients with cardiac diseases on evolution CT. Cardiac structure and function were analysed visually and quantitatively (left ventricular ejection fraction, left ventricular myocardial mass, patency of coronary arteries, perfusion of left ventricular myocardium). The CT findings were compared with echocardiographic and angiographic findings. RESULTS: Cardiac structure, functional parameters and disorders of myocardial contraction were clearly detectable by ultrafast CT, which proved inferior in assessing cardiac valves. The patency of the first and second third of normal main coronary arteries could be estimated correctly. The estimation of the distal third, of obstructed coronary arteries and of the role of collaterals was impossible. Ten of 16 areas of myocardial infarction showed low or no enhancement. CONCLUSIONS: Ultrafast CT excellently reflects cardiac structure and function. It is an alternative to echocardiography. In view of the results of coronary artery patency one can hope that part of cardiac catheterisation would be avoidable in future.

Adult↗
PubMed1994

[Detection of coronary calcification by ultrafast CT compared with coronary angiography].

The angiographical findings of 24 patients with coronary artery disease were compared with qualitative and quantitative detection of coronary calcification by ultrafast CT. Doubts concerning the capabilities of the ultrafast CT for a screening of coronary artery disease arise when the results of one third false positive and false negative findings are considered. Variations in the quantification of coronary calcification were too great to allow a realistic assessment of the degree of stenosis of the coronary arteries.

Adult↗
PubMed1993

Effects of N-terminal truncations upon chloroplast NADP-malate dehydrogenases from pea and spinach.

Using the purification procedure of Fickenscher and Scheibe (Biochim. Biophys. Acta 749 (1983), 249-254) and a modification of the method, we produced a series of NADP-MDH forms from spinach and pea-leaf extracts that were characterized by a stepwise shortening of the N-terminal sequences. Limited proteolysis of the enzymes resulted in the generation of even shorter forms. Immunoprecipitation of the NADP-MDH from crude extracts revealed that the sequences of the intact enzymes from pea, spinach and maize started at a position (Ser) identical with that established for the Sorghum enzyme (Crétin, C., et al. (1990) Eur. J. Biochem. 192, 299-303). Spinach NADP-MDH isolated by conventional methods was shown to represent the intact form. Thus, the kinetic, regulatory and structural properties of the various truncated forms could be compared with those of an intact form. Removal of 5 or 11 amino acids, as occurred during isolation of the pea NADP-MDH, was without any significant effect. The enzymes were all dimeric and still exhibited the characteristic redox-regulatory properties. However, removal of 31 and 37 amino acids using aminopeptidase K resulted in the formation of active monomers characterized by only slightly lowered affinities towards the substrates, a shift of their pH optimum from 8 to 7, the loss of oxaloacetate inhibition and an increased maximal velocity. Although these forms lacked most or all of the N-terminal extra-peptide, including the 2 cysteines involved in redox-modification, they were still sensitive to the redox-potential. However, the low concentration of thiol required for immediate and complete restoration of any lost activity (40 mM beta-mercaptoethanol) suggested that this reaction might not be relevant for redox-regulation in vivo.

Amino Acid Sequence↗
PubMed1993

Analysis of biophysical differences between oxidized and reduced chloroplast NADP-malate dehydrogenase.

Various properties of purified chloroplast NADP-malate dehydrogenase were analyzed with respect to the redox state of the light/dark-modulated enzyme. The reduced enzyme is less resistant to heat, but the instability can be overcome by the addition of the coenzyme NADPH. Similarly, instability of the reduced NADP-MDH at high pH is alleviated by NADPH. The kinetics and protection characteristics of the alkylation of accessible thiols of NADP-MDH are used to describe the location of essential thiols relative to the active site, since again the coenzyme protects the active enzyme very effectively from inactivation by alkylation. The increased hydrophobicity of the reduced as opposed to the oxidized enzyme becomes apparent as the loss of activity from solutions due to adsorption to plastic surfaces. The kinetics and the solvent dependency of this process are analyzed and discussed, both from the practical (recovery of the purified enzyme) and the physiological point of view (in vivo protein/protein and protein/membrane interactions). The oxidized NADP-MDH has a lower tendency to bind to solid surfaces. NADP(H) efficiently prevents adsorption of the reduced form. Macromolecular solvents (polyethylene glycol), detergents (Triton X-100), or competing proteins also protect this otherwise very hydrophobic form from irreversible loss due to adsorption. Ribulosebisphosphate carboxylase/oxygenase and polyethylene glycol 10,000, however, used as competing substances only keep the oxidized, not the reduced, NADP-MDH in solution.

Chloroplasts↗
PubMed1992

[Densitometry determination of coronary flow rates using digital subtraction angiography (DSA). Methods, multiple examinations and interobserver comparison].

In invasive diagnostics of coronary heart disease (CHD), three each DSA examinations of the left coronary artery were performed at 2-minute intervals in ten patients subsequent to conventional examination by means of a left-side cardiac catheter and coronary angiography. While placing the patient in left anterior oblique (60 degrees) position, 6 ml each of ionic contrast medium were injected mechanically with a flow of 4 ml/sec at a pacemaker-induced heart rate of 100/min. Examinations were performed according to a standard mode and were evaluated via the image analysing computer APU of the Philips DVI-DSA system. The purpose of this approach was to analyse the examination conditions and a new improved evaluation algorithm in respect of stability, feasibility and sensitivity. 17 series were evaluated by two examiners who were independent of each other. The interobserver differences obtained were between 5% at the time of maximum density (Tmax) and 25% with exponential downward slope of the curve (lambda), with reference to the median value in each case. Scatter of the individual examinations around the median value of all the three DSA runs is 11 to 17% with the exception of lambda. A significant rise can be proven in the RCX region for the curve slope rise parameters "slope" and "RFL2". We interpret this as a genuine 1.2 to 1.3 fold regional flow increase due to the residual effect of the contrast medium. At the same time, this can be interpreted as an indicator for the good sensitivity of the method.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

[A densitometric method for the assessment of myocardial perfusion using digital subtraction angiography].

The aim of the method presented is the quantitative description of the perfusion of the myocardium. In the framework of the invasive diagnostics of the coronary heart disease with catheterization of the left heart, ventriculography and coronarography in Seldinger's technique in 50 patients (35 of them well to be evaluated) subsequently DSA-investigations of the left coronary artery (LCA) were performed by means of the DVI-2 CV system (Philips) and densitometrically evaluated with the help of the analytic processing unit (APU). In injection by hand of 4 and 6 ml, respectively, visotrast 370 in each case 10-15 DSA-pictures in LAO 60 degrees-projection were possible. For a differentiated evaluation the total myocardium was subdivided into 12 partial areas. The densitometric analysis consisted in the calculation of time-density curves over all areas and their description by suitable parameters: density maximum (DMAX) and its moment TMAX, elevation of the curve SLOPE at 50% of DMAX, the elevation time AZEIT as well as measure for the exponential decrease of the curve after the maximum LAMBDA. For special questioning the parameters of the 12 areas were concentrated according to the main supply areas of the anterior interventricular branch (RIVA), the circumflex branch (RCX) and the apex of the heart, respectively. In the interobserver comparison the statistical analysis of the results showed deviations lower than 10% (except LAMBDA). Significant correlations were found between the body-weight and the applied quantity of contrast remedies, respectively, and the parameters DMAX and AZEIT.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

[Venous digital subtraction angiography of the left ventricle in comparison with conventional angiography].

In 42 patients with coronary heart disease within a left heart catheterization by means of coronarography and conventional angiocardiography in each case before and after GTN digital subtraction angiographies of the left ventricle were performed with central venous injection of 20 ml visotrast with a flow of 16-18 ml/s. A DVI2-CV system of the firm Philips served as investigation device. In general between the angiocardiography and the digital subtraction angiographies the following results were obtained for EF 0.81, EDV 0.71, and ESV 0.88. When evaluating only the finally examined 22 patients the correlations improve for all parameters (EF: 0.89, EDV: 0.82, ESV: 0.90). Furthermore is was shown that the volumes are underestimated by 8-10%. The quantification of the regional movement of the wall according to the radial axis method did not results in any significant differences between the digital subtraction angiographies and the angiocardiography. The effects of GTN on the global and regional functional parameters appear somewhat more distinct in the digital subtraction angiographies than in the angiocardiography and are partly significant only in the first one. The influence of the experience of the investigator, the cardial state of the patient and other influential factors on the quality of the digital subtraction angiocardiographies are described and discussed. Therefore we regard the digital subtraction angiography as method of choice in indications to right heart catheterization without coronary angiography.

Adult↗
PubMed1990

[Secular acceleration and the electrocardiography in childhood and adolescence].

As a consequence of advanced growth episondes and an increase in the final height of adolescents, resulting in changes in the cardiovascular system, an "acceleration" of electrocardiographic parameters and special morphological features of the ECG can be observed. The trend towards a closer relation between ECG parameters and body height than age, as seen in our probands as well as in the literature, reflects the influence of acceleration on the electrocardiogram.

Adolescent↗
PubMed1988

[Determination of global left ventricular functional parameters with intraventricular digital subtraction angiography in coronary disease].

Left heart catheterisation, coronarography and conventional angiocardiography of the left ventricle (ACG) [30 degrees right anterior oblique; 45 ml contrast medium (Visotrast) with a flow of 12 ml per sec.] was performed in 86 patients with coronary heart disease. Additionally intraventricular digital subtraction angiography (DSA) was performed, using a Philips-device (DVI 2 CV). For DSA 15 ml contrast medium (Visotrast) was injected with a flow of 8 ml per sec. 73 examinations were selected for the study. The aim of the study was to compare the usefulness and applicability of ACG und DSA for ventriculography. There were no significant differences between enddiastolic (EDV) and endsystolic (ESV) volumes as well as ejection fractions (EF) determined by ACG and DSA. Results of the analysis of correlation were rEDV = 0.85;rESV = 0.93;rEF = 0.80. The increase of the end-diastolic pressure after ACG was determined with 7 Torr (mean), after DSA with less than 2 Torr (mean). According to these results we would prefer intraventricular DSA to conventional ACG, provided the technical equipment is available. This is concluded despite the fact that in single cases considerable differences were found between the volumes estimated by ACG and those determined by DSA. These differences were analysed in detail. The main advantages of the DSA are the by far smaller inconvenience for the patients, the rare occurrence of provoked extrasystoles and the fast and easy analysis of the ventriculographies by means of the implemented image processing programmes.

Cardiac Output↗