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Biomedical subjects

U Steinhoff

Publications and source records attributed to U Steinhoff.

At least 19 recordsLinked to original sources
PubMed2004

Spatial distribution of cardiac magnetic vector fields acquired from 3120 SQUID positions.

An extended measurement of the magnetic vector field of the human heart is presented. It is acquired by sequential recordings, shifting a 16 SQUID vector magnetometer across 195 positions over a healthy subject's thorax. The magnetocardiographic (MCG) signals were synchronized using a simultaneously measured ECG channel. The registration of the field extends over a volume of 1000 mm x 600 mm x 420 mm sampled at 3120 SQUID positions. We present diagrams of the vector amplitude of selected points in 6 planes at increasing distances from the frontal thorax. Each plane contains 76 vector points. Additionally, we measured the vector field at 126 points lateral to the chest. At the edge points of the measurement volume, the absolute value of the magnetic vector signal amplitude exceeds 0.3 pT in all measurement points. The dataset provides an excellent base to study dedicated MCG detection or rejection methods. Examples where rejection of the heart signal is necessary are magnetoencephalography, magnetoneurography and fetal MCG. The knowledge of the spatio-temporal distribution of the magnetic vector field of the heart supports the development and comparison of multi-SQUID systems and will be used to create new MCG interpretation and representation algorithms.

Body Surface Potential Mapping↗
PubMed2004

A sensor configuration for a 304 SQUID vector magnetometer.

A novel SQUID vector magnetometer system is introduced which has been specially designed for the use inside the strongly magnetically shielded room BMSR-2 of PTB. The system is housed in a dewar with a flat bottom and an inner diameter of Ø 250 mm. The SQUIDs are arranged so that in addition to the usually measured Z-component of the field the horizontal magnetic fields are measured too. A total of 304 DC-SQUID magnetometers are divided up into 19 identical modules. The 16 low-Tc SQUIDs of each module are located in such a way that an estimation of the magnetic field in all three dimensions is possible at three points inside the module. The 57 SQUIDs of the lowest Z plane of all modules form a hexagonal grid with a base length of 29 mm. The design criteria and the physical principle behind the complex SQUID arrangement are explained.

Electromagnetic Fields↗
PubMed2004

[Structured concept for the establishment of a broad and ambulatory care of patients with type 2 diabetes: one-year evaluation of a regional teaching organization].

BACKGROUND: The increasing prevalence of diabetes mellitus and its long-term complications are associated with an expanding social medical problem. In order to originate an established teaching and training program on a physician-based level in short time, three specialist diabetes centers from Lübeck transferred their concept to a diabetes organization based on 17 physicians who had only rarely undertaken any diabetes teaching before. We investigated the achievement and effectiveness of this concept in a prospective multicenter evaluation one year after the patients had received structured diabetes teaching by the organization. PATIENTS AND METHODS: Physicians and their teaching staff were trained by the specialists from the diabetes centers according to an official agreement. Patients were treated by each practice, while the diabetes teaching was done centrally by the organization through a diabetes assistant/dietician based on a modified official diabetes teaching and training program (ZI-program). 230 of 250 patients (120 male, 110 female) were reinvestigated one year after they had received the teaching. The group consisted of 179 non-insulin-treated (NIB; 94 via physicians, 85 via specialists) and 51 insulin-treated (IB; 19 via physicians, 32 via specialists) participants. RESULTS: The average age of NIB was 60.4+/-9.8 years, while IBs were 68.8+/-7.3 years old. HbA (1c) values were reduced in both groups, NIB and IB, by approximately 1% (NIB: 7.59+/-1.97% to 6.59+/-1.84%; IB: 8.47+/-1.35% to 7,36+/-1,38 %; p < 0,001). In the NIB-group the BMI was reduced by 0,64+/-0,14 kg x m (-2), whereas it was increased in the IB-group by 0.33+/-0.24 kg x m(-2) (NIB: 30.55+/-0.40 to 29.91+/-0.39 kg x m(-2), p < 0.001; IB: 28.83+/-0.74 to 29.16+/-0.75 kg x m(-2), p = 0.82). CONCLUSION: The transfer of established teaching and training concepts of specialist diabetes centers to a newly founded, physician-based diabetes organization resulted in a broad, effective and long-lasting medical care of patients with type 2 diabetics treated without or with insulin. The results are superior to those of other evaluations based on diabetes training ZI-programs.

Aged↗
PubMed2002

Imaging characteristics of different multichannel magnetocardiographic systems.

In this study a comparison of multichannel magnetocardiographic systems is performed with respect to the "detectable" information content. We investigate the lead-field matrices, the slope of the singular values and the source spaces of three different devices: the VectorView (Neuromag: magnetometer-gradiometer mixed device) of the BioMag Laboratory, Helsinki University Central Hospital (HUCH), the arrangement of electronically coupled magnetometers of the Physikalisch-Technische Bundesanstalt Berlin (PTB) and a virtual sensor geometry which was optimized for an improved slope of the singular values at the Institute of Biomedical Engineering, Karlsruhe.

Adult↗
PubMed2001

Magnetocardiographic mapping of QRS fragmentation in patients with a history of malignant tachyarrhythmias.

BACKGROUND: The identification of patients at increased risk for ventricular tachycardia or ventricular fibrillation (VT/VF) and sudden cardiac death has consequences for therapeutic options and thus may reduce mortality in patients with coronary artery disease (CAD). HYPOTHESIS: We hypothesized that the intra-QRS fragmentation in magnetocardiographic recordings is increased in patients with CAD and with a history of VT/VF. METHODS: Multichannel magnetocardiography (MCG) was carried out in 34 healthy controls, 42 patients with CAD without a history of VT/VF, and 43 patients with CAD and with a history of VT/VF. The intra-QRS fragmentation was quantified by a new fragmentation score. Its spatial distribution was investigated using two-dimensional (2-D) contour maps according to the sensor position of the 49-channel magnetogradiometer. RESULTS: Patients with CAD and with a history of VT/VF had significantly increased QRS fragmentation compared with patients with CAD without VT/VF or controls (72.9+/-37.5, 48.5+/-14.3, and 42.5+/-7.8, respectively: p <0.05). The area of high fragmentation in 2-D contour maps was twice as large in patients with than in those without a history of VT/VF (represented by the number of MCG channels with high fragmentation: 26.3+/-15.5 vs. 12.4+/-9.9, p<0.0001). Patients prone to VT/VF could be identified with a sensitivity of 64% and a specificity of 90%. CONCLUSION: In patients with CAD and with a history of VT/VF, intra-QRS fragmentation is increased and the area of high fragmentation in 2-D contour maps is enlarged. These findings may be helpful in identifying patients with CAD at risk for malignant tachyarrhythmias.

Adult↗
PubMed2000

Identification of post-myocardial infarction patients with ventricular tachycardia by time-domain intra-QRS analysis of signal-averaged electrocardiogram and magnetocardiogram.

A new time-domain analysis method, which quantifies ECG/MCG intra-QRS fragmentation, is applied to parts of the QRS complex to identify post-myocardial infarction patients with ventricular tachycardia. Three leads of signal-averaged electrocardiograms and nine leads of magnetocardiograms were band-pass filtered (74 Hz to 180 Hz). The filtered signals showed fragmentation in the QRS region, which was quantified by the number of peaks M and a score S, that is the product of M and the sum of the peak amplitudes. Both parameters were determined for the first 80 ms of the QRS complex and the total QRS complex in each channel. For classification, the mean-values of the parameters M and S of the three electrical leads and the nine magnetic leads were calculated. Late potential and late field analyses were performed for the same signals. 31 myocardial infarction patients were included, 20 of them with a history of documented ventricular tachycardia (VT). Identification of VT patients using the SAECG led to better results (sensitivity 95%, specificity 91%) considering the entire QRS complex than with the standard late potential analysis suggested by Simson (sensitivity 90%, specificity 73%). For the SAMCG and the entire QRS complex results using the parameters S and M are also better (sensitivity 95%, specificity 100%) than for the late field analysis (sensitivity 90% and specificity 100%). For the first 80 ms, the performance of the parameters M and S is only slightly decreased.

Adult↗
PubMed2000

Rapid neutrophil response controls fast-replicating intracellular bacteria but not slow-replicating Mycobacterium tuberculosis.

Being one of the first cells to invade the site of infection, neutrophils play an important role in the control of various bacterial and viral infections. In the present work, the contribution of neutrophils to the control of infection with different intracellular bacteria was investigated. Mice were treated with the neutrophil-depleting monoclonal antibody RB6-8C5, and the time course of infection in treated and untreated mice was compared by using intracellular bacterial species and strains varying in virulence and replication rate. The results indicate that neutrophils are crucial for the control of fast-replicating intracellular bacteria, whereas early neutrophil effector mechanisms are dispensable for the control of the slow-replicating Mycobacterium tuberculosis.

Animals↗
PubMed1999

Variable immune response against a developmentally regulated self-antigen.

We studied the reactivity of T and B cells against a soluble form of the glycoprotein of vesicular stomatitis virus (VSV-G) which was expressed in a transgenic mouse (line 23) under the control of the hormone regulated beta-lactoglobulin promoter. Transgenic mice expressed VSV-G in the thymus, spleen, mammary gland and lung. VSV-G transcripts in the thymus varied with age, i.e., expression was high early in life and decreased with age. VSV-G transgenic mice immunized with recombinant vaccinia virus expressing VSV-G exhibited normal VSV-G-specific IgM levels, but a 30-fold reduction in IgG response, indicating functional VSV-G-specific B cell activity but impaired T helper cell responses. Interestingly, VSV-G-specific T helper cell activity was reduced only early (4-10 weeks) and late in life (>40 weeks) but was normal in between. Double transgenic mice expressing VSV-G and a VSV-G-specific TCR (line 23x7) demonstrated that TCR transgenic CD4(+) T cells were partially deleted in early life, but then gradually repopulated the periphery and remained constant. These findings suggest that in line 23 two different mechanisms regulated levels of the immune response: clonal reduction/deletion of VSV-G-specific T cells during early life followed by peripheral anergy at a later stage.

Aging↗
PubMed1999

Autoimmune intestinal pathology induced by hsp60-specific CD8 T cells.

Due to their ubiquitous distribution and high degree of structural similarity, heat shock proteins (hsp) are potential target antigens in autoimmune diseases. Here, we describe induction of intestinal inflammation following transfer of hsp60-reactive CD8 T cells into mice. Inflammatory reactions were MHC class I dependent and developed primarily in the small intestine. IFN gamma and TNF alpha, as well as gut-derived hsp60, were elevated at sites of T cell infiltration. Intestinal lesions were drastically reduced in mice lacking receptors for TNF alpha. Pathology also developed in germ-free mice, indicating recognition of host-derived hsp60 by CD8 T cells. This report demonstrates that CD8 T cells with defined antigen specificity cause intestinal inflammation, emphasizing a link between infection and autoimmune disease.

Animals↗
PubMed1999

Magnetocardiographic analysis of the two-dimensional distribution of intra-QRS fractionated activation.

The spatial distribution of high-frequency components in magnetic signals during the QRS complex of the human heartbeat was investigated. Cardiomagnetic signals were recorded simultaneously using 49 first-order magnetogradiometer channels of a multi-SQUID system with a low noise power density. The QRS fragmentation score S, as a measure of the fragmentation of the bandpass-filtered QRS complex, was examined for its sensitivity and specificity to discriminate 34 healthy volunteers, 42 post-myocardial infarction patients and 43 patients with coronary heart disease and with a history of malignant sustained ventricular tachycardia or ventricular fibrillation. The multichannel information was visualized by two-dimensional mapping of the score values of the single channels. By averaging the score values for the seven central channels, S7, the score values of all 49 channels, S49, and calculating the standard deviation for all 49 channels, D49, a higher sensitivity and specificity for detecting patients with ventricular tachycardia (VT) or ventricular fibrillation (VF) was reached than by analysis of a single channel. Combination of these parameters furnishes a sensitivity of 90% and a specificity of 70% for identifying patients prone to VT/VF. The results were compared with diagnostic information obtained from the QRS duration of the signal as well as with results obtained by modified QRS integral mapping.

Adult↗
PubMed1999

Value of magnetocardiographic QRST integral maps in the identification of patients at risk of ventricular arrhythmias.

It has been shown that regional ventricular repolarization properties can be reflected in body surface distributions of electrocardiographic QRST deflection areas (integrals). We hypothesize that these properties can be reflected also in the magnetocardiographic QRST areas and that this may be useful for predicting vulnerability to ventricular tachyarrhythmias. Magnetic field maps were obtained during sinus rhythm from 49 leads above the anterior chest in 22 healthy (asymptomatic) control subjects (group A) and in 29 patients with ventricular arrhythmias (group B). In each subject, the QRST deflection area was calculated for each lead and displayed as an integral map. The mean value of maximum was significantly larger in the control group A than in the patient group B (1,626+/-694 pTms vs. 582+/-547 pTms, P<0.0001). To quantitatively assess intragroup variability in the control group A and intergroup variability of the control and patient groups, we used the correlation coefficient r and covariance sigma. These indices showed significantly less intragroup than intergroup variation (e.g., in terms of sigma, 28.0x10(-6)+/-12.3x10(-6) vs. 3.4x10(-6)+/-12.5x10(-6), P<0.0001). Each QRST integral map was also represented as a weighted sum of 24 basis functions (eigenvectors) by means of Karhunen-Loeve transformation to calculate the contribution of the nondipolar eigenvectors (all eigenvectors beyond the third). This percentage nondipolar content of magnetocardiographic QRST integral maps was significantly higher in the patient group B than in the control group A (13.0%+/-9.1 % vs. 2.6%+/-2.0%, P<0.0001). Discriminations between control subjects and patients with ventricular arrhythmias based on magnitude of the maximum, covariance sigma, and nondipolar content were 90.2%, 90.2%, and 86.3% accurate, with a sensitivity of 89.7%, 93.1%, and 75.9%, and a specificity of 90.9%, 86.4%, and 100%. We have shown that magnitude of the maximum and indices of variability and nondipolarity of the magnetocardiographic QRST integral maps may predict arrhythmia vulnerability. This finding is in agreement with earlier studies that used body surface potential mapping and suggests that magneticfield mapping may also be a useful diagnostic tool for risk analysis.

Adult↗
PubMed1998

Altered intestinal immune system but normal antibacterial resistance in the absence of P-selectin and ICAM-1.

ICAM-1 and P-selectin are adhesion molecules that regulate leukocyte migration, extravasation to inflammatory sites, and other immune cell interactions. T cell-mediated resistance against acute infection with Listeria monocytogenes and chronic infection with Mycobacterium bovis Calmette-Guérin bacillus was investigated in mutant mice lacking P-selectin and/or ICAM-1. Mice deficient in P-selectin (Psel-/-), ICAM-1 (ICAM-/-), or the combination of both (Psel-/- x ICAM-/-) showed normal bacterial clearance, comparable delayed-type hypersensitivity reactions, and equivalent memory T cell responses. Additionally, the distribution of alpahbeta vs gammadelta T lymphocyte populations was examined. Normal lymphocyte distributions were noted in thymus, spleen, and blood, whereas mutant mice showed marked alterations in the intestinal intraepithelial (i-IEL) and lamina propria lymphocytes. Differences in i-IEL populations were reflected functionally by differential lytic activities and cytokine productions of i-IEL populations from mutant mice. Despite these changes within the mucosal immune system of mutant mice, their resistance against oral infection with L. monocytogenes was apparently unimpaired. These findings demonstrate that P-selectin and ICAM-1 are critically involved in the shaping of lymphocyte populations of the gut but have only a minor influence on systemic and regional host defense against intracellular bacteria.

Animals↗
PubMed1998

Fragmentation of bandpass-filtered QRS-complex of patients prone to malignant arrhythmia.

The structure of high-frequency components of electric and magnetic signals from the heart during the depolarisation phase is investigated. After averaging and broadband filtering with a binomial bandpass filter (37 Hz-90 Hz), the fragmentation of the QRS-complex is quantified. The number of extrema M and a new score value S are calculated from the signals of three electrical leads and one magnetic lead of 23 healthy subjects, 23 patients with coronary heart disease (CHD) without reported event of ventricular tachycardia or fibrillation at the time of measurement, and eight patients with CHD who have suffered from malignant tachycardia. For the parameter M, the sensitivity and specificity for healthy subjects against patients with CHD and ventricular tachycardia for the magnetic lead (the best electric lead) are 100% (75%) and 100% (100%). For the magnetic lead (best electric lead) and parameter S, the sensitivity and specificity are 100% (75%) and 95.6% (100%).

Electrocardiography↗
PubMed1996

Magnetometry of evoked fields from human peripheral nerve, brachial plexus and primary somatosensory cortex using a liquid nitrogen cooled superconducting quantum interference device.

Superconducting Quantum Interference Devices (SQUIDs) can be used to detect neuromagnetic fields evoked in the peripheral and central nervous system. Up to now, such measurements had to be based on SQUIDs with a low critical temperature (Tc) requiring liquid helium cooling. Recent improvements in high-Tc SQUID technology relying on liquid nitrogen cooling led to a significant reduction in the system's noise level. Hare, first high-Tc recordings of weak neuromagnetic fields are demonstrated. In particular, along the entire somatosensory afferent pathway including peripheral nerves, brachial plexus and primary somatosensory neocortex evoked neuromagnetic activities were detected using conventional recording parameters for bandwidth and number of averages. This opens up a wide perspective for cost-effective high-Tc magnetometry in clinical neuroscience.

Brachial Plexus↗
PubMed1995

Antiviral protection by vesicular stomatitis virus-specific antibodies in alpha/beta interferon receptor-deficient mice.

The role of innate, alpha/beta interferon (IFN-alpha/beta)-dependent protection versus specific antibody-mediated protection against vesicular stomatitis virus (VSV) was evaluated in IFN-alpha/beta receptor-deficient mice (IFN-alpha/beta R0/0 mice). VSV is a close relative to rabies virus that causes neurological disease in mice. In contrast to normal mice, IFN-alpha/beta R0/0 mice were highly susceptible to infection with VSV because of ubiquitous high viral replication. Adoptive transfer experiments showed that neutralizing antibodies against the glycoprotein of VSV (VSV-G) protected these mice efficiently against systemic infection and against peripheral subcutaneous infection but protected only to a limited degree against intranasal infection with VSV. In contrast, VSV-specific T cells or antibodies specific for the nucleoprotein of VSV (VSV-N) were unable to protect IFN-alpha/beta R0/0 mice against VSV. These results demonstrate that mice are extremely sensitive to VSV if IFN-alpha/beta is not functional and that under these conditions, neutralizing antibody responses mediate efficient protection, but apparently only against extraneuronal infection.

Animals↗