ß-Glutamine-mediated self-association of transmembrane ß-peptides within lipid bilayers.

Transmembrane ß-peptide helices and their association in lipid membranes are still widely unexplored. We designed and synthesized transmembrane ß-peptides harboring different numbers of d-ß3-glutamine residues (hGln) by solid phase peptide synthesis. By means of circular dichroism spectroscopic measurements, the secondary structure of the ß-peptides reconstituted into unilamellar vesicles was determined to be similar to a right-handed 314-helix. Fluorescence spectroscopy using d-ß3-tryptophan residues strongly suggested a transmembrane orientation. Two or three hGln served as recognition units between the helices to allow helix-helix assembly driven by hydrogen bond formation. The association state of the transmembrane ß-peptides as a function of the number of hGln residues was investigated by fluorescence resonance energy transfer (FRET). Therefore, two fluorescence probes (NBD, TAMRA) were covalently attached to the side chains of the transmembrane ß-peptide helices. The results clearly demonstrate that only ß-peptides with hGln as recognition units assemble into oligomers, presumably trimers. Temperature dependent FRET experiments further show that the strength of the helix-helix association is a function of the number of hGln residues in the helix.

Visualisation of biochemical network simulations with SimWiz.

SimWiz is a Java package that aims at visualising data resulting from different kinds of biochemical systems simulations in a clear and easy-to-survey way. In addition, information regarding the topology of the biochemical network is preserved by this visualisation. This is achieved by animating a graphical representation of the respective biochemical network.

Auditory brainstem implant: part I. Auditory performance and its evolution over time.

OBJECTIVE: Evaluation of auditory performance and its evolution over time in patients with the auditory brainstem implant. STUDY DESIGN: Prospective study. SETTING: Tertiary referral center. PATIENTS AND METHODS: Between May 1996 and April 2000, 14 patients with neurofibromatosis type 2 underwent implantation with a multichannel auditory brainstem implant. Auditory performance data were obtained in 13 patients who had used their device on a regular daily basis for 1 to 41 months (average 19 months). Hearing evaluation was based on the results of four tests (vowel confusion, consonant confusion, Freiburger numbers, and speech-tracking test), which were performed with and without lip-reading at regular intervals after device activation. RESULTS: 12 patients received auditory sensation through the auditory brainstem implant immediately after device activation. In one patient, because of postoperative electrode migration, device activation was not successful. In this case, after the electrode array was repositioned, activation was successful. The results of the audiovisual mode 2 weeks after device activation revealed a lip-reading enhancement above the chance level in about 50% of the patients in the vowel confusion and speech-tracking tests and in 70% of the patients in the consonant confusion test. Lip-reading enhancement improved within the first 6 months and then entered a plateau phase, which was more prominent in the monosyllabic vowel and consonant tests. In the auditory alone mode, more than half of the patients showed their first positive result in the vowel test 3 months after device activation, but it took about 6 months until half of the patients revealed a result above the chance level in the consonant and Freiburger numbers tests. Open set speech recognition in the auditory alone mode (in the speech-tracking test) was not common and happened relatively late (within 1 year or later). DISCUSSION AND CONCLUSION: Although auditory sensation appeared immediately after device activation, a period of 6 months was necessary for relearning and adaptation of the central auditory system to the altered form of auditory information presented by the auditory brainstem implant.

Auditory brainstem implant in auditory rehabilitation of patients with neurofibromatosis type 2: Hannover programme.

An auditory brainstem implant (ABI) is indicated for patients suffering from bilateral neural deafness. The most affected patients are those with neurofibromatosis type 2 (NF2). An implantation is possible either at the same time as, or after, surgical removal of an acoustic neuroma. This paper demonstrates the results of eight out of 11 patients with NF2, seven of whom received an ABI after tumour removal. Pre-operatively, all of them were deaf. Post-operatively, the first fitting served to determine the individual stimulation parameters for each electrode. The stimulation-dependent side-effects were eliminated by reducing the stimulus intensity without causing negative effects on the hearing with the ABI. Only in one case was an open set understanding achieved within the first year. However, all patients had a better speech understanding when they combined their hearing with the ABI and their lip-reading abilities. There is no correlation between the performance with ABI and the tumour size or the duration of deafness.

[Position identification in knee joint endoprosthesis]. / Lageerkennung in der Kniegelenkendoprothetik.

In this paper we present a method for measuring the wear of the polyethylene inlay in knee joint endoprostheses from standard X-ray images. Our approach is to estimate the spatial position of the tibial and femoral components of the prostheses from their contours in the X-ray image. When we know the exact shape of these two components, we can calculate the minimal spatial distance between them which approximates the remaining thickness of the inlay. First results show that this approach might provide sufficient accuracy for the given task.

Postoperative results for adults and children implanted with the Clarion device.

Our experience with deaf adults and children who have received the Clarion multistrategy implant are very encouraging. Because of certain programming characteristics of the current device, access to the compressed analog coding strategy has been limited. We expect to see this change in the near future. The CIS strategy, however, appears to provide patients with important, full-spectrum speech information so that they accommodate to the auditory sensations rapidly and begin to interpret sound into meaningful speech within a short time.