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Biomedical subjects

H Jäger

Publications and source records attributed to H Jäger.

At least 37 records · Page 2Linked to original sources
PubMed1999

Interrelations between EEG frequency components in sedated intensive care patients during burst-suppression period.

The EEG during basic sedation and burst patterns during electroencephalic burst-suppression patterns (BSP) were analyzed. The aim of EEG analysis was the characterization and quantification of the interrelations between distinct frequency components in both states of sedation. The data for the investigations were derived from the routine EEG derivations of 12 patients with various neurosurgical diseases. It can be demonstrated that the degree of interrelation (amplitude modulation) between a low-frequency component (0-2.5 Hz) and oscillations with higher frequency (3-7.5 and 8-12 Hz) is increased in burst patterns during BSP compared with the EEG during basic sedation. It can be concluded that the degree of interrelations depends on the sedation depth induced by hypnotic drugs.

Adolescent↗
PubMed1999

[Interventional treatment of arteriosclerotic carotid stenosis].

PURPOSE: Angioplasty and stent placement of atherosclerotic internal carotid artery stenosis (ICA) are evaluated based on own experiences with the method and reports of other groups and are compared with vascular surgery. METHODS: ICA-stenoses of more than 70% were treated by angioplasty and stent placement mainly using the Wallstent. The patients had follow-up examinations with an angiogram after 6 months and colour-coded duplex ultrasound at regular intervals. RESULTS: In 633 patients 799 ICA stenoses were treated, 70% of them were symptomatic and 30% asymptomatic. In 99% of the patients the stenoses could be removed with a reduction of the degree of stenosis from 82% to 12%. Transient neurological deficits occurred in 5% and permanent deficits in 2.7% of the patients with decreasing incidence over the years. Five-year patency was 91.6%. CONCLUSION: Endoluminal treatment of atherosclerotic ICA stenosis is an efficient procedure which can be applied in patients, in whom carotid surgery is indicated, but also in cases with an increased operative risk or inoperability from technical or medical reasons.

Angioplasty, Balloon↗
PubMed1999

[Cytomegalovirus (CMV) retinitis in AIDS. Gancilovir implantation in comparison with systemic therapy].

INTRODUCTION: Untreated CMV retinitis with AIDS leads to blindness; therefore, a life-long virostatic treatment is required. It can either be administered systemically or locally, as there are different advantages and disadvantages. When treating patients we aim at therapy that preserves vision without diminishing quality of life. It should induce as few drug-induced side effects as possible and not shorten the patient's life expectation. METHODS AND RESULTS: A total of 111 patients (150 eyes) with systemic maintenance treatment were compared retrospectively with 33 patients (62 eyes) that received a ganciclovir implant only as maintainance therapy and no additional systemic treatment. Patients with an implant showed a prolonged interval of nonprogression of retinitis than patients receiving systemic treatment. Patients with unilateral retinitis are at higher risk of developing bilateral disease in the implant group than in the systemically treated group. Manifestation of extraocular disease was equal in both groups. Local treatment with the implant does not shorten patient survival time. CONCLUSION: Local treatment with the ganciclovir implant means quality of life for patients and also safe protection of the affected eye. Extraocular disease and survival time are not influenced adversely by local treatment. However, primarily unilateral involved patients show higher risk for bilateral disease in the implant group than in the systemically treated group.

AIDS-Related Opportunistic Infections↗
PubMed1999

New approaches for the detection and analysis of electroencephalographic burst-suppression patterns in patients under sedation.

An automatic EEG pattern detection unit was developed and tested for the recognition of burst-suppression periods and for the separation of burst from suppression patterns. The median, standard deviation and the 95% edge frequency were computed from single channels of the EEG within a moving window and completed by the continuous computation of frequency band power via an adapted Hilbert resonance filter. These parameters were given to the inputs of two hierarchically arranged artificial neural networks (NNs). The output signals of NNs indicate the suppression and burst phases. The burst recognition was focused on the precise recognition of the burst onset. In subsequent processing steps the time course of percentages of burst patterns within their corresponding burst-suppression-phases was calculated and the time locations of burst onsets can be used to trigger an averaging for a burst-related analysis. The data for our investigations were derived from the routine EEG derivations of 12 patients with various neurosurgical diseases. A group-related training of the NNs was realized. For the group-related trained NNs EEG data for 6 patients were used for training and the data of 6 other patients for testing the classification performance of the pattern recognition units. Additionally, the reliability of the detection algorithm was tested with data of two patients with convulsive state, resistant to treatment, and burst-suppression like pattern EEC.

Adolescent↗
PubMed1999

Lack of absorption of didanosine after rectal administration in human immunodeficiency virus-infected patients.

The feasibility of rectal administration of didanosine (DDI) was studied in six human immunodeficiency virus-infected patients. After oral intake of a DDI solution (100 mg/m2 of body surface area) combined with an antacid (Maalox), pharmacokinetic parametric values were in accordance with previously published data; the mean +/- standard deviation for terminal half-life was 59.5 +/- 15.0 min, that for peak concentration was 5.2 +/- 3.9 mumol/liter, and that for the area under the time-concentration curve (AUC) was 494 +/- 412 min.mumol/liter. After rectal administration of a similarly prepared DDI solution (100 mg/m2 of body surface area), plasma DDI levels were below the detection limit (0.1 mumol/liter) at all time points in five of the six patients, and in the remaining patient the AUC after rectal application was only 5% of that after oral administration. We conclude that oral administration of DDI cannot be easily replaced by rectal application.

Administration, Rectal↗
PubMed1999

[Strengthening the patients' position--a new challenge to public health].

Prevention and health promotion are well-established strategies to reduce the demand for health care. Nevertheless efforts to encourage the empowerment of consumers vis-à-vis the providers of health-care are relatively new in Germany. Programmes intended to improve a person's level of confidence in dealing with chronic illness have been shown to lower costs. The potential for reducing demand for unnecessary interventions may save money and increase the quality of provided health care. The views of consumers and their personal experiences are crucial in establishing a more effective quality management in the German health care system in Germany. At present patients are not always sufficiently involved in the process of clinical decision-making and often their knowledge does not enable them to assess the quality of services rendered. In comparison with other European countries the position of German patients is rather weak. The backing of patients' interests by insurance companies is more developed in Belgium, self-organisation of patients is established in Switzerland and, with strong government support, in the Netherlands (Kranich, 1997). However in Germany there is now growing interest in providing support for patients' participation in the choice of treatment, quality of health care and decision-making strategies for health problem management. The German Ministry of Health is currently working on a Patients' Charter to guarantee patients' rights. The Public Health Service could play its role in representing patients' interests more intensively. Health-insurance companies could concentrate more on educating the consumer in order to encourage better informed decisions and to reduce the frequency of unnecessary health care procedures. The benefits yielded by self-management of health problems (not to be confused with self-treatment), of chronic disease or disability are well-documented and may ultimately even lower medical costs. In this article, various approaches to stimulate patients' empowerment are suggested with the context of the German Health Care System.

Delivery of Health Care↗
PubMed1999

Adaptable preprocessing units and neural classification for the segmentation of EEG signals.

In this contribution, a methodology for the simultaneous adaptation of preprocessing units (PPUs) for feature extraction and of neural classifiers that can be used for time series classification is presented. The approach is based upon an extension of the backpropagation algorithm for the correction of the preprocessing parameters. In comparison with purely neural systems, the reduced input dimensionality improves the generalization capability and reduces the numerical effort. In comparison with PPUs with fixed parameters, the success of the adaptation is less sensitive to the choice of the parameters. The efficiency of the developed method is demonstrated via the use of quadratic filters with adaptable transmission bands as preprocessing units for the segmentation of two different types of discontinuous EEG: discontinuous neonatal EEG (burst-interburst segmentation) and EEG in deep stages of sedation (burst-suppression segmentation).

Coma↗
PubMed1999

[Adolescence and "sexual health"].

Sexual health is a substantial part of the general social, cultural and personal well-being of adolescents. Sustainable sexual education is only likely if the general self-confidence and competence of adolescents are strengthened and if programmes are integrated into the socio-cultural context of communal development. Health professionals may diagnose existing problems but they are seldom competent in resolving the underlying social dilemmas. Nevertheless, the health system offers a unique opportunity of addressing adolescents and influencing their behaviour patterns. The risk approach in the prevention of sexually transmitted infections and unwanted pregnancies often ignores the pressing personal fears, anxieties and problems seen by the adolescents themselves. An integrated approach to Sexual Health should consider the views of adolescents as a priority and offer opportunities to address personal questions, worries and anxieties. Rather than medical experts, adolescents need mediators and professional guides to find their own way through the social and health network. They need to consult persons who can respond to their intimate concerns and give independent evidence-based information on health procedures and prevention.

Adolescent↗
PubMed1998

Treatment with protease inhibitors associated with peripheral insulin resistance and impaired oral glucose tolerance in HIV-1-infected patients.

BACKGROUND: The use of protease inhibitors in the treatment of HIV-1 infection is associated with the new onset of diabetes mellitus, hyperlipidaemia and lipodystrophy. It is unclear whether these findings are coincidental or whether they reflect a causative effect of protease inhibitors. OBJECTIVE: To evaluate the effect of treatment with protease inhibitors on insulin sensitivity, oral glucose tolerance and serum lipids in HIV-infected patients in order to determine whether treatment with protease inhibitors can cause peripheral insulin resistance. DESIGN: Cross-sectional controlled study in HIV-infected patients treated with protease inhibitors to assess insulin sensitivity, oral glucose tolerance and changes in serum lipids. METHODS: Sixty-seven patients treated with protease inhibitors, 13 therapy-naive patients and 18 HIV-negative control subjects were tested for insulin sensitivity (intravenous insulin tolerance test). In a subgroup of 24 treated patients, oral glucose tolerance was determined. Serum lipids prior to and under treatment with protease inhibitors were compared. RESULTS: Patients on protease inhibitors had a significantly decreased insulin sensitivity when compared with therapy-naive patients (median, 75 and 156 micromol/l/min, respectively; P < 0.001). All treated patients with impaired (n=4) or diabetic (n=9) oral glucose tolerance, and four out of 11 patients with normal glucose tolerance showed peripheral insulin resistance; all therapy-naive patients had normal insulin sensitivity. Treatment with protease inhibitors led to a significant increase in total triglycerides and cholesterol in the 67 treated patients (median increase, 113 and 37 mg/ml, respectively). CONCLUSION: Treatment with protease inhibitors is associated with peripheral insulin resistance, leading to impaired or diabetic oral glucose tolerance in some of the patients, and with hyperlipidaemia. Overall, there is a large variation in the severity and clinical presentation of protease inhibitor-associated metabolic side-effects.

Adult↗
PubMed1998

Topology of subunit a of the Escherichia coli ATP synthase.

The antigenic determinants of mAbs against subunit a of the Escherichia coli ATP synthase were mapped by ELISA using overlapping synthetic decapeptides. For two of the mAbs the epitopes are E4NMTPQD10 (GDH 14-5C6) and V29DPQ32 (GDH 8-8B3). Binding of these mAbs to membrane vesicles of different orientation revealed that both epitopes are accessible in vesicles with inside-out orientation. These results demonstrate that at least the N-terminal amino acids 1-32 of subunit a are located at the cytoplasmic side of the membrane. A further determination of the topology of subunit a was performed by inserting the reporter epitope DYKDDDDK (FLAG epitope) at different positions of the polypeptide chain. 10 of 13 insertions led to a functional F0F1 ATP synthase and allowed specific detection of the modified subunit a by immunoblotting using an mAb against the FLAG epitope. In addition, polyclonal anti-FLAG IgG was applied for the recognition of the mutant FLAG epitope DYKDDVDK. Cells carrying this mutant FLAG epitope at the C terminus of subunit a were able to grow on succinate as sole carbon and energy source, revealing a functional ATP synthase, in contrast to those carrying the original FLAG epitope at the same position. Binding studies with membrane vesicles of different orientation and anti-FLAG Ig demonstrated that both termini of the protein are located at the cytoplasmic side of the membrane, indicating that an even number of membrane-spanning segments is present in subunit a. In addition, insertion of two FLAG epitopes in tandem after K66, or one epitope after H95, and Q181 revealed that the polypeptide regions including these residues are accessible from the cytoplasmic surface of the membrane. These results support the view that the polypeptide chain of subunit a traverses the membrane six times.

Amino Acid Sequence↗
PubMed1998

Regulation of mammalian Shaker-related K+ channels: evidence for non-conducting closed and non-conducting inactivated states.

1. Using the whole-cell recording mode we have characterized two non-conducting states in mammalian Shaker-related voltage-gated K+ channels induced by the removal of extracellular potassium, K+o. 2. In the absence of K+o, current through Kv1.4 was almost completely abolished due to the presence of a charged lysine residue at position 533 at the entrance to the pore. Removal of K+o had a similar effect on current through Kv1.3 when the histidine at the homologous position (H404) was protonated (pH 6.0). Channels containing uncharged residues at the corresponding position (Kv1.1: Y; Kv1.2: V) did not exhibit this behaviour. 3. To characterize the nature of the interaction between Kv1.3 and K+o concentration ([K+]o), we replaced H404 with amino acids of different character, size and charge. Substitution of hydrophobic residues (A, V and L) either in all four subunits or in only two subunits in the tetramer made the channel insensitive to the removal of K+o, possibly by stabilizing the channel complex. Replacement of H404 with the charged residue arginine, or the polar residue asparagine, enhanced the sensitivity of the channel to 0 mM K+o, possibly by making the channel unstable in the absence of K+o. Mutation at a neighbouring position (400) had a similar effect. 4. The effect of removing K+o on current amplitude does not seem to be correlated with the rate of C-type inactivation since the slowly inactivating G380F mutant channel exhibited a similar [K+]o dependence as the wild-type Kv1.3 channel. 5. CP-339,818, a drug that recognizes only the inactivated conformation of Kv1.3, could not block current in the absence of K+o unless the channels were inactivated through depolarizing pulses. 6. We conclude that removal of K+o induces the Kv1.3 channel to transition to a non-conducting 'closed' state which can switch into a non-conducting 'inactivated' state upon depolarization.

3T3 Cells↗
PubMed1998

[Interventional radiology in central venous obstructions. Dilatation--stent implantation--thrombolysis].

PURPOSE: Venous congestion of the superior or inferior caval system has to be considered as a medical emergency. The results of various recanalization procedures and their utility are analyzed. PATIENTS AND METHODS: 176 patients with superior and 28 with inferior caval obstruction were treated with Gianturco-Z (n = 39) and Wall Stents (n = 207) respectively. Balloon venoplasty was performed prior to stent implanation. In 27 cases, local thrombolysis with urokinase was employed. RESULTS: Interventional procedures were successful in 198 and without success in 6 patients. In most patients, symptoms were relieved during or early after recanalization. No major complications were found. DISCUSSION: Balloon angioplasty with stent placement and local thrombolysis are successful in the treatment of superior and inferior caval obstruction. Self-expanding Wallstents are superior to Gianturco-Z-stents. Oncologists should be made familiar with this type of treatment.

Adolescent↗
PubMed1998

[High-flow priapism following blunt perineal trauma. Interventional therapy].

A 10-year old boy developed an arteriocavernosal fistula with a permanent penile erection (high-flow priapism) after a blunt perineal trauma. The diagnosis was established by Doppler ultrasound, blood gas analysis and angiography. A conservative treatment attempt with penile cooling and puncture of the cavernosal corpera with blood aspiration and etilefrine instillation failed to resolve the priapism. An embolization of both bulbocavernosal arteries was followed by an immediate detumescence. Normal functional erection was preserved. No recurrence was observed during a follow-up of 6 months.

Accidents, Traffic↗
PubMed1998

Multimodal time-variant signal analysis of neonatal EEG burst patterns.

It can be shown that dominant rhythmic signal components of neonatal EEG burst patterns (discontinuous EEG in quiet sleep) are characterized by a quadratic phase coupling (bispectral analysis), i.e. a multiplicative interaction (connection) between the underlying electrophysiological processes can be assumed. By means of pattern recognition algorithms as well as time-variant spectral and coherence analysis, a so-called "initial wave" (narrow band rhythm within a frequency range of 3-12 Hz) can be demonstrated within the first part of the burst pattern. The detection of this signal component and of the quadratic phase coupling is more successful in the frontal region. By means of amplitude demodulation of the "initial wave" the phase coupling can be attributed to an amplitude modulation. The results were derived from 6 neonates (20 burst patterns for each neonate; 8-channel recordings). A 16-channel EEG-recording was analyzed for one neonate.

Electroencephalography↗
PubMed1997

Analysis of the interrelations between a low-frequency and a high-frequency signal component in human neonatal EEG during quiet sleep.

It can be shown that dominant rhythmic signal components of neonatal EEG burst patterns (discontinuous EEG in quiet sleep) are characterised by a quadratic phase coupling (bispectral analysis). A so-called 'initial wave' (narrow band rhythm within a frequency range of 3-12 Hz) can be demonstrated within the first part of the burst pattern. The detection of this signal component and of the phase coupling is more successful in the frontal region. By means of amplitude demodulation of the 'initial wave' and a subsequent coherence analysis the phase coupling can be attributed to an amplitude modulation, i.e. the envelope curve of the 'initial wave' shows for a distinct period of time the same qualitative course as the signal trace of a 'lower' frequency component (0.75-3 Hz). The results were derived from six neonates (20 burst patterns for each neonate; 8 channel recordings).

Brain Mapping↗
PubMed1997

[Viral load--significance for individualized therapy].

The treatment of HIV infection/AIDS has changed dramatically because of a new pathophysiological understanding of this disease. The most important laboratory parameter for the management of antiretroviral therapy is the direct measurement of virus load in plasma. In Germany 11 different medications are available to the patient for reduction of his viral load in blood and possibly tissues, i.e. lymph-nodes. The majority (about 2/3) of physicians begin to treat with double combination therapy. Protease inhibitors are an important addition to the therapeutic arsenal.

Anti-HIV Agents↗